Karvonen Target Heart Rate Calculator (Heart Rate Reserve)

Enter height and weight to get your BMI and category (underweight / normal / overweight / obese).

Estimate daily BMR and TDEE using Mifflin-St Jeor or Harris-Benedict, with calorie targets for cutting and bulking.

Estimate body fat percentage using the US Navy circumference formula (neck, waist, plus hip for women).

Suggest ideal bedtimes or wake times based on 90-minute sleep cycles, so you wake up between cycles instead of mid-deep-sleep.

Estimate daily water intake from body weight, exercise duration and climate so you stay hydrated without overdoing it.

Compute pace per km / per mile from distance and time, or project finish time from a target pace — covers 5K, 10K, half- and full-marathon distances.

Compute 5 training heart rate zones from age and optional resting HR using the Karvonen formula (Z1 warm-up to Z5 max effort).

Estimate lean body mass (LBM), fat mass and body fat % from height, weight and sex using the Boer, Hume and James formulas.

Split a daily calorie target into grams of carbs, protein and fat at any macro ratio.

Estimate one-rep max from a sub-maximal lift (weight × reps) with Epley, Brzycki, Lombardi and Lander formulas, plus a 50–95% intensity training table.

Estimate body surface area from height and weight using the Mosteller, Du Bois, Haycock and Boyd formulas — commonly used in drug-dosing, chemotherapy and cardiac-index calculations.

Project a finish time at one distance from a known time at another distance using the classic Riegel formula T₂ = T₁ × (D₂/D₁)^1.06.

Compute mean arterial pressure from systolic and diastolic blood pressure with clinical bands and pulse-pressure context: MAP = DBP + (SBP − DBP)/3.

Compute cumulative smoking exposure in pack-years from cigarettes per day and years smoked, with lung-cancer-screening thresholds.

Divide waist by hip circumference and check the WHO risk bands — a quick screen for central obesity and cardiovascular risk.

Use METs, body weight and duration to estimate calories burned for common activities (running, hiking, swimming, cycling and more).

Pick the dose (mg) and the time you drank it; the calculator uses the standard ~5-hour caffeine half-life to project how many milligrams remain hour-by-hour, including the level at bedtime.

Bergman’s BAI estimates body-fat percentage from hip circumference and height alone (BAI = hip ÷ height^1.5 − 18) — no scale required.

Enter age, sex, height and weight to compare all five activity levels side-by-side — instantly see the daily calories you need to maintain weight.

Estimate blood alcohol concentration (BAC %) with the Widmark formula from drinks consumed, body weight, sex and hours elapsed — and compare against the Hong Kong 0.05% drink-driving limit.

Enter your distance covered in a 12-minute run to estimate VO₂ max and read off the age/sex fitness category.

Enter your bodyweight and training goal to get a science-backed daily protein range (g/day) and per-meal split, based on RDA, ISSN and ACSM/AND/DC guidelines.

Enter your last menstrual period (LMP) date and average cycle length to estimate the next ovulation day, fertile window and next period.

Estimate total body water (in litres) and the percentage of body weight using the Watson formula based on age, sex, height and weight.

Enter step count, height (auto-derives stride length) and body weight to estimate distance walked (km / mi), stride length, calories burned and your daily activity tier.

Enter a food's glycemic index (GI) and grams of carbs per serving to compute glycemic load GL = GI × carbs ÷ 100 — a better predictor of real blood-sugar response than GI alone.

Convert HbA1c (%) to estimated average glucose (eAG) in both mg/dL and mmol/L — and back again — to help diabetes and prediabetes patients read their lab reports.

Enter height, weight and body-fat percentage to compute Fat-Free Mass Index (FFMI) and the height-adjusted FFMI used to gauge muscularity.

Enter height and sex to compare the four classic ideal-body-weight formulas (Devine, Robinson, Miller, Hamwi), with their average and a ±10 % healthy-weight band.

Select 0–2 points for each of the five APGAR signs (Appearance / Pulse / Grimace / Activity / Respiration) to get the total APGAR score (0–10) and clinical band (normal / moderately depressed / severely depressed).

Pick eye-opening (1–4), verbal (1–5) and motor (1–6) responses to compute the Glasgow Coma Scale total (3–15) with mild / moderate / severe banding.

Enter systolic (SBP) and diastolic (DBP) blood pressure; the tool returns the pulse pressure and mean arterial pressure (MAP), then classifies the result as low / normal / elevated using the < 40, 40–60 and > 60 mmHg bands — the textbook signal for cardiovascular risk on a routine BP report.

Enter serum creatinine, age and sex; the tool applies the 2021 NKF / ASN-recommended CKD-EPI formula (race-free) to estimate glomerular filtration rate (eGFR) and classifies the result into CKD stages G1–G5 — the standard reading of a kidney-function lab report.

Enter age, weight, serum creatinine and sex; the tool applies the 1976 Cockcroft–Gault formula to estimate creatinine clearance (CrCl, mL/min) — still the FDA- and EMA-required formula for renal dose adjustment in most drug labels.

Enter waist circumference and height in any units; the tool returns the waist-to-height ratio (WHtR) and classifies it against the universal "keep your waist to less than half your height" cut-off (< 0.5) — a more sensitive central-obesity signal than BMI.

Computes the pediatric maintenance IV fluid rate (mL/hr and mL/day) from body weight using the Holliday-Segar 4-2-1 rule — the standard since the original 1957 publication.

Enter total cholesterol, HDL and triglycerides; the Friedewald equation (LDL = TC − HDL − TG / 5 or / 2.2 SI) estimates LDL-C and grades the result by NCEP ATP III risk bands.

Enter your current weight, target weight and daily calorie deficit; the tool uses the "≈ 3 500 kcal per lb of body fat" rule of thumb to project the number of weeks and the expected date you will reach your goal — a sanity check for setting a sustainable pace.

Enter pre / post-exercise body weight, fluids consumed and session length; the tool returns sweat rate per hour (L/h) and a suggested fluid intake every 15 minutes per the ACSM hydration guidelines — used by runners, cyclists, footballers and recruits.

Enter a drink's volume (ml) and alcohol content (ABV %); the tool converts to standard drinks using each region's definition (US 14 g, UK 8 g, AU/HK 10 g, JP 20 g of pure alcohol) and compares with WHO and national low-risk guidelines (e.g. ≤ 10 drinks/week).

Enter height and waist circumference; the tool applies the Thomas (2013) Body Roundness Index BRI = 364.2 − 365.5·√(1 − ((WC/2π) ⁄ (0.5·h))²). BRI tracks visceral fat and metabolic-disease risk more closely than BMI — a JAMA 2024 study linked BRI to cardiovascular mortality.

Enter visual acuity in Snellen (20/20, 20/40, etc.), metric Snellen (6/6, 6/12), LogMAR or decimal; the tool returns the other three formats with reference thresholds for driving licences and the legal-blindness cut-off — the standard conversion for ophthalmology, optometry and driving / occupational medicals.

Tick the burned regions (head, anterior / posterior torso, arms, legs, perineum) and the patient age group (adult / child); the tool applies Wallace's Rule of Nines to return total body-surface-area burned (%TBSA) and shows the Parkland fluid-resuscitation target — the standard field tool in emergency medicine, fire-rescue and first-aid.

Enter body weight, sex and the powerlifting total (squat + bench + deadlift, in kg or lb); the tool applies the Wilks 2020 coefficients to return the Wilks score — the standard way to compare powerlifters across body-weight classes and sexes, and the basis of best-lifter awards in IPF, USAPL and many federations.

Enter total carbohydrates, dietary fibre and sugar alcohols (per serving); the tool returns Net Carbs = total carbs − fibre − ½ × sugar alcohols. The standard keto / low-carb / diabetic-diet metric for absorbable carbs per serving.

Enter heart rate (HR) and stroke volume (SV); the tool computes cardiac output Q = HR × SV (L/min) and, given body surface area (BSA), the cardiac index CI = Q / BSA. Core hemodynamic math for emergency medicine, cardiology and nursing.

Enter weight and body-fat percentage; the tool returns BMR via the Katch-McArdle formula (BMR = 370 + 21.6 × lean body mass in kg) and TDEE after an activity multiplier. More accurate than Mifflin-St Jeor for lean and athletic body types where fat mass varies widely.

Enter the child's weight (kg), prescribed dose (mg ⁄ kg ⁄ dose or mg ⁄ kg ⁄ day), dosing frequency and adult-equivalent maximum; the tool returns the per-dose and total-daily amounts and flags when the adult cap is exceeded. The bread-and-butter weight-based dosing framework used in paediatrics worldwide.

Enter wet-bulb, globe and dry-bulb temperatures; the tool returns WBGT via the ISO 7243 formula 0.7·Tnwb + 0.2·Tg + 0.1·Tdb and classifies the result against the NIOSH / US military flag system (white / green / yellow / red / black) — the international standard for assessing heat-stroke risk in sport and occupational settings.

Enter cadence (steps per minute) and stride length (cm or m); the tool returns running speed (km/h, mph), pace (min/km, min/mi) and distance per minute — handy for runners on Garmin, Apple Watch and Strava tuning cadence vs stride.

Enter height and wrist circumference; the tool applies Grant's index r = height ÷ wrist circumference to classify body frame (small / medium / large) — used to adjust "ideal weight" estimates and reflects bone-structure differences that a single BMI value cannot.

Enter inseam (the floor-to-crotch length); the tool returns the recommended saddle height using LeMond's formula (inseam × 0.883, bottom-bracket to top-of-saddle) and the Hamley/Holmes method (~109% inseam to pedal), together with the 25°–35° knee-angle range for reference.

Enter treadmill speed (km/h or mph) and incline (%); the tool uses the ACSM running metabolic equation to return the equivalent flat-ground pace (min/km and min/mile) so you can compare indoor and outdoor effort.

Pick a fasting protocol (14/10, 16/8, 18/6, 20/4, OMAD, etc.) and your last-meal time; the tool returns when you can break the fast next, tomorrow's eating-window start and end, and total weekly fasting hours — useful for planning an IF schedule.

Enter your target hours per night plus the actual hours slept each of the past 7 nights; the tool returns total accumulated sleep debt (hours), average nightly shortfall, and how many consecutive "+1 h" nights are needed to clear it.

Enter your age; the tool reports the recommended sleep range from the US National Sleep Foundation's 2015 consensus guidelines (newborns 14–17 h, infants 12–15 h, preschoolers 10–13 h, adults 7–9 h, older adults 7–8 h) and a suggested bed-and-wake schedule.

Enter your height and a target BMI (e.g. 22.0); the tool computes the matching weight from W = BMI × (height/100)² in both kg and lb, plus how much you need to gain or lose from your current weight.

Enter the carbohydrate grams in a meal, pre- and post-meal glucose, the rapid-acting insulin units used and the glucose target; the tool applies the 500/TDD rule with the insulin sensitivity factor (ISF) to give a personalised ICR (g of carb per 1 U of insulin) and a suggested bolus.

Enter the total running time (hh:mm:ss) and distance (km or mile); the tool returns pace per kilometre, pace per mile, average speed (km/h, mph) and per-km / per-mile split tables — a quick way to compare training and race performance.

Enter your peak heart rate at end of exercise (HR_peak) and 1-minute post-exercise heart rate (HR_1min); the tool computes HRR = HR_peak − HR_1min — a cardiovascular fitness indicator from Cleveland Clinic (Cole et al., NEJM 1999): HRR ≤ 12 bpm is high-risk, 18–24 is average, ≥ 25 is good / athletic.

Enter your FTP (Functional Threshold Power, watts); the tool applies the Coggan 7-zone model to give the upper and lower bounds (Z1 Active Recovery → Z7 Neuromuscular Power) for every training zone — works for indoor trainers, road riding and Zwift sessions alike.

Enter your total daily insulin dose (TDD); the tool returns ISF — the mg/dL or mmol/L drop per 1 unit of rapid-acting insulin — via the 1800 / 1500 / 100 rule, a starting point for correction-bolus dosing in type-1 diabetes management.

Enter the control-event rate (CER) and the experimental-event rate (EER); the tool returns the absolute risk reduction ARR = CER − EER, the relative risk reduction RRR and the number needed to treat NNT = 1 / ARR — the cornerstone metrics for reading clinical trials and evidence-based medicine.

Enter events and non-events in the exposed and control arms (the classic 2×2 table); the tool returns the risk ratio (RR), odds ratio (OR), risk difference (RD) and their 95 % confidence intervals — the core statistics for cohort and case-control epidemiology.

Enter the patient weight in kg; the tool applies the Holliday-Segar 4-2-1 rule to compute the maintenance IV fluid rate (mL/hr) and total daily volume (mL/day) — the standard bedside estimate for paediatric and adult inpatient fluid orders, useful for clinicians, nurses and pharmacists.

Enter the measured QT interval (ms) and heart rate (bpm) (or RR interval); the tool reports QTc using all four standard corrections — Bazett, Fridericia, Framingham and Hodges — and flags values outside the normal range. Essential for ECG interpretation and monitoring of QT-prolonging drugs.

Enter total volume, infusion time and the tubing drop factor (gtt/mL; macro 10/15/20, micro 60); the tool returns the required drops per minute (gtts/min) and the equivalent mL/hr — the standard bedside calculation for nurses, ER and IV-therapy clinicians.

Enter serum Na⁺, Cl⁻ and HCO₃⁻ (optionally K⁺ and albumin); the tool reports the anion gap AG = Na − (Cl + HCO₃), the albumin-corrected gap and a classification of metabolic acidosis (high vs. normal gap) — a staple for emergency, ICU and nephrology interpretation of blood-gas and electrolyte panels.

Enter age and the tool applies the empirically-fit Tanaka et al. (2001) formula HRmax = 208 − 0.7 × age to estimate maximum heart rate (bpm), compares it with the traditional 220 − age rule and shows 50–90% intensity zones — the standard reference for running, cycling, HIIT and cardiac-rehab target heart rates.

Enter your height and the activity type (walking / jogging / running); the tool applies the standard regression coefficients (Pichler / NSCA) to estimate average stride length (cm per step) and converts it back to steps per km and steps per mile — useful for calibrating a pedometer, planning a walking workout or turning a step-count goal into real distance.

Enter age and sex; the tool returns the recommended daily Adequate Intake (AI) of dietary fiber in grams per the US Institute of Medicine (IOM 2005) reference tables — covering children, adults and older adults — plus the practical 14 g per 1000 kcal cross-check.

Enter daily energy intake and choose a guideline (WHO 5 % or 10 % of energy, AHA men 36 g / women 25 g); the tool reports the daily added-sugar ceiling in grams and teaspoons, plus its share of total calories — for sugar control, diabetes management and weight loss.

The tool shows daily sodium and salt limits per the major guidelines — WHO (adults < 2000 mg = < 5 g salt), US FDA (< 2300 mg), UK NHS (< 2400 mg = < 6 g salt) and the American Heart Association (ideal < 1500 mg) — adjusted by age and (optionally) hypertension / cardiovascular risk, and compares any single-food sodium amount against the daily budget.

Enter your total time in bed (lights off → out of bed), estimated fall-asleep latency and total awake time after onset; the tool returns sleep efficiency % and bands (< 75 % poor, 75–84 % fair, 85–89 % good, ≥ 90 % excellent), with the standard CBT-i sleep-restriction guidance keyed to those bands.

Enter HbA1c (%) or three-month average blood glucose (mg/dL or mmol/L); the tool applies the ADAG 2008 linear equation eAG (mg/dL) = 28.7 × A1C − 46.7 to convert in either direction — the standard cross-reference for self-monitored diabetes care, pre-visit estimation and lab-report interpretation.

Computes a daily fiber target using the U.S. National Academy of Medicine recommendation of 14 g per 1000 kcal (or a sex-/age-based table lookup) — a universal, simple guide for planning a high-fiber diet.

Enter an infant's weight (kg) and the number of feeds per day; the tool returns daily total formula volume and per-feed volume using international paediatric guidance (≈ 150 mL/kg/day, typical range 140–200 mL/kg/day) — a universal first-pass tool for parents of healthy term infants.

Look up the daily calcium target from the US NIH / IOM DRI tables (different for children, adults, pregnancy and seniors); enter age and sex / life stage and the tool reports the mg-per-day goal together with food equivalents (cups of milk, slices of cheese, servings of greens) — the standard reference for bone-health planning and child growth.

Enter age, sex, life stage (pregnancy / lactation / menstruating) and diet type (omnivore / vegetarian); the tool reports the daily iron target in mg using the NIH RDA tables — vegetarians multiplied by 1.8 to reflect lower bioavailability — the reference tool for anemia prevention, women of reproductive age and pregnant users.

Enter age, body weight and pregnancy status; the tool reports your daily caffeine safe limit in mg using EFSA / FDA / AAP guidance (adults 400 mg, pregnant 200 mg, adolescents 3 mg / kg), then converts it into equivalent cups of coffee, tea, cola and energy drinks — the standard tool for managing day-to-day caffeine intake.

Enter age, sex and life stage (pregnancy / lactation); the tool returns the daily magnesium mg target using the NIH RDA tables (adult men 400–420 mg, women 310–320 mg) and converts it into common food portions — an essential mineral for nerves, muscles, heart rhythm and bones.

Enter age, sex, life stage and your preferred unit (IU or mcg); the tool returns the daily vitamin D target from the NIH / IOM Dietary Reference Intakes — infants 400 IU AI, ages 1–70 600 IU and > 70 years 800 IU. It also shows the adult Tolerable Upper Intake Level (UL = 4 000 IU / day) and equivalent food servings (salmon, cod-liver oil, fortified milk, egg yolks, UV-exposed mushrooms).

Enter age, sex and life stage; the tool returns the daily potassium mg target from the US NASEM 2019 DRI / NIH ODS Potassium Fact Sheet AI table (adult men 3 400 mg, women 2 600 mg, pregnancy 2 900 mg, lactation 2 800 mg) and converts it into common high-potassium food servings (banana, baked potato, avocado, spinach, white beans).

Enter age, sex, life stage and smoking status; the tool returns the daily vitamin C mg target from the NIH / IOM Vitamin C Fact Sheet RDA (adult men 90 mg, women 75 mg, smokers +35 mg) and converts it into common food portions.

Enter age, sex and life stage; the tool returns the daily zinc mg target from the NIH / IOM Zinc Fact Sheet RDA (adult men 11 mg, women 8 mg, pregnancy 11 mg, lactation 12 mg) — central to immunity, wound healing and the sense of taste / smell.

Enter age, sex and life stage; the tool returns the daily selenium µg target from the NIH ODS Selenium Fact Sheet RDA (adults 55 µg, pregnancy 60 µg, lactation 70 µg, UL 400 µg) — a trace mineral essential to antioxidant defence, thyroid-hormone synthesis and immunity.

Enter age, sex and life stage; the tool returns the daily folate target in µg DFE from the NIH ODS Folate Fact Sheet RDA (adults 400, pregnancy 600, lactation 500, supplement UL 1000 µg / day) — the B-vitamin central to cell division, red-blood-cell formation and the prevention of fetal neural-tube defects.

Enter your training goal (maximal strength, hypertrophy, muscular endurance, power) and load intensity (% 1RM); the tool returns evidence-based rest-interval seconds between sets and the matching set / rep ranges, per NSCA Essentials of Strength Training (4th ed.) and ACSM guidelines.

Look up your daily vitamin B12 RDA (μg/day) by age, sex and pregnancy / lactation status using NIH ODS values, with B12 amounts in common foods and supplementation notes for vegetarians and vegans.

Look up your daily iodine RDA (μg/day) by age, sex and pregnancy / lactation status using NIH ODS values, with iodine content in iodised salt, seafood and common foods — guarding against deficiency (goitre) and excess (thyroid dysfunction).

Look up your daily vitamin A RDA (μg RAE/day) and tolerable upper intake (UL) by age, sex and pregnancy / lactation status using NIH ODS values; converts retinol and β-carotene to RAE so you can avoid deficiency (night blindness) and retinol overdose.

Paste a list of RR intervals (in ms, comma- / space- / newline-separated); the tool returns RMSSD = √(mean((RR_{i+1} − RR_i)²)), SDNN, mean heart rate, and an interpretation following the 1996 Task Force HRV standards — handy for sanity-checking HRV figures from a Garmin, Apple Watch or Polar device.

Enter the shoe type (max-cushion, daily trainer, racing flat and more), runner weight tier and miles already logged; the tool uses the 300–500 mile sports-medicine wear-out range to return the miles remaining and a months-of-use estimate at your current cadence — handy for avoiding knee pain and plantar fasciitis from worn midsoles.

Caffeine's half-life averages about 5 hours — a 200 mg morning coffee still leaves ~100 mg in your blood at 5 pm and ~50 mg by 11 pm. Enter the dose and time taken to see exactly how much is still circulating when you try to sleep.

BMI Prime = BMI ÷ 25 — expresses any BMI as a fraction of the normal-weight upper limit, so 1.00 means right at the cap and 1.20 means 20 % above it. Enter height and weight to read it instantly.

Spherical equivalent SE = Sphere + (Cylinder ÷ 2) collapses a cylindrical (astigmatism) prescription into a single spherical power — routinely used for ordering contact lenses, refractive-surgery screening, and basic vision reports. Also returns the vertex-compensated corneal-plane power for high Rx.

Enter pre-pregnancy height and weight (for BMI), gestational week and current weight; the tool returns the recommended total weight-gain range and weekly rate for singleton or twins based on the Institute of Medicine (IOM/NAM 2009) guidelines, comparing to actual gain.

Enter current age and sex; using the WHO Global Health Observatory period life table, the tool estimates remaining life expectancy and projected age at death assuming present-day mortality.

Using the dermatology 2 mg/cm² standard, work out how many grams of sunscreen (≈ the "shot-glass rule") you need for full body or each zone, then estimate reapplication interval from the classic "SPF × natural burn time" formula.

Enter trail distance, elevation gain and walking pace; using outdoor educator Paul Petzoldt's "energy miles" rule (+2 miles per 1,000 ft gain), the tool returns effective distance, estimated time and a difficulty rating.

Enter race distance, projected finish time and carb intake target (g/h); based on the 30–90 g/h sports nutrition range, returns how many gels and at what spacing.

Enter your 12-minute run distance (m or mi), age and sex; the tool estimates VO₂max via Cooper's 1968 JAMA formula and maps it to a six-band age/sex fitness classification.

Enter age (and optional resting HR); compare HRmax estimates from Fox (220−age), Tanaka, Gellish and the Nes / HUNT3 formula side-by-side, plus Karvonen training-zone bpm ranges.

Enter DEXA-scan T-score (and optional Z-score); classifies as normal / osteopenia / osteoporosis per WHO 1994 + ISCD 2019 criteria and shows relative fracture-risk multiplier.

Enter your best 20-minute average power (watts) to get your FTP (= 20-min × 0.95) and the seven Coggan training zones (Z1 Recovery through Z7 Neuromuscular).

Enter the total water volume (ml) — get the grams of salt, glucose (or substitute sucrose) and optional potassium chloride needed for a WHO/UNICEF low-osmolarity ORS, the standard rehydration recipe for diarrhoea worldwide.

Enter your age and habitual reading distance — get a quick estimate of the near-add power (+0.50 to +3.00 D) for off-the-shelf reading glasses, based on the Hofstetter 1944 accommodation formula and standard optometric guidance.