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Corrected Calcium (for Albumin) Calculator

About half of serum calcium is bound to albumin, so a low albumin drags the measured total calcium down even when the biologically active free (ionised) calcium is actually normal. This tool uses the classic Payne correction to "adjust" total calcium back to an albumin of 4.0 g/dL (SI: 40 g/L), giving a truer read on calcium status. It supports both mg/dL and mmol/L units.

Corrected calcium

9.2 mg/dL

Normal

Reference range

Low
< 8.5
Normal
8.510.5
High
> 10.5

Measured

8.0 mg/dL

Correction (Δ)

+1.2 mg/dL

Formula: mg/dL — corrected = measured + 0.8 × (4.0 − albumin g/dL); SI — + 0.02 × (40 − albumin g/L). Payne, BMJ 1973. Educational only — it does not replace an ionised-calcium test or clinical judgement.

Formula

mg/dL: corrected Ca = measured Ca + 0.8 × (4.0 − albumin g/dL) mmol/L: corrected Ca = measured Ca + 0.02 × (40 − albumin g/L)

Frequently asked

Why does calcium need to be "corrected"?

Because about half the calcium in blood is bound to albumin. When albumin is low (e.g. malnutrition, liver disease, hospitalised patients) the measured total calcium reads low even though the active free calcium may be normal. The correction estimates what total calcium would be at a normal albumin, so you do not mistakenly diagnose hypocalcemia.

How is corrected calcium different from ionised calcium?

Ionised (free) calcium directly measures the biologically active calcium and is the most accurate marker, but needs special sampling and equipment. Corrected calcium is only an albumin-based estimate — quick and convenient but less accurate. When the result is critical, rely on ionised calcium.

What if albumin is higher than normal?

If albumin is above 4.0 g/dL (40 g/L) the formula corrects downward, so corrected calcium is slightly lower than the measured value. This is less common (e.g. severe dehydration) but the formula still applies.

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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.

Maffetone 180-Formula Maximum Aerobic Heart Rate

Compute your MAF maximum aerobic heart rate (zone-2 ceiling) using Dr. Phil Maffetone's 180-formula: 180 minus age ± a correction based on health and training status.

Hair / Beard Growth Time Calculator

Enter current and target hair (or beard) length and the calculator returns how many months — at the population-average growth rate of ≈ 1.25 cm/month for scalp hair and ≈ 1 cm/month for beards — it will take to reach the goal. Useful for post-chemo regrowth, post-shave timeline, gender-transition grow-out and post-surgical hair recovery planning.

Adult Height Predictor (Mid-Parental Formula)

Enter both parents' heights and the child's sex; the Tanner mid-parental formula estimates the child's adult height with a ±8.5 cm 95 % confidence interval.

Caffeine Safe Daily Dose Calculator (mg/kg by body weight)

Enter body weight and population (healthy adult, pregnant, adolescent, child) — using EFSA / FDA / ACOG mg/kg ceilings the tool returns today's daily ceiling and the single-dose ceiling, and converts both into equivalent cups / cans of drip coffee, espresso, black & green tea, cola and energy drink.

Electrolyte / ORS Home Recipe Calculator

Enter the finished volume you want to mix — using the WHO low-osmolarity ORS recipe the tool returns grams of table salt, sugar plus optional KCl and trisodium citrate, with no-scale teaspoon equivalents.

Jump Rope Length Calculator (by Height)

Enter your height (cm or inches) and skill level (beginner, intermediate, speed) — the tool returns recommended rope length handle-to-handle. Formula: height × 1.5 (beginner) or height + 30 cm (speed-rope).

Blood Pressure Category Classifier (AHA / ACC 2017)

Enter systolic and diastolic blood pressure (mmHg); the tool returns the AHA / ACC 2017 category — Normal, Elevated, Hypertension Stage 1, Hypertension Stage 2 or Hypertensive Crisis — used by clinicians worldwide for adult screening.

Daily Vitamin K Intake Calculator (DRI / Adequate Intake)

Enter age, sex and life stage; the tool returns the *Adequate Intake* (AI) for vitamin K (K1 phylloquinone + K2 menaquinone) in µg / day per the US Institute of Medicine DRI tables and converts the target into the grams (or tablespoons) of kale, spinach, natto, broccoli or olive oil you would need to hit it.

mEq ↔ mg Electrolyte Converter (Na, K, Ca, Mg, Cl)

Pick an electrolyte ion (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and more); enter milliequivalents (mEq) or milligrams (mg); the tool uses mg = mEq × (atomic mass ÷ valence) to convert both directions — matching IV-drip prescriptions, oral supplements, drug labels and electrolyte amounts on food labels.

Stride Length Calculator (from Height, Walking / Running)

Enter height, sex and mode (walking, jogging, sprinting); the tool uses the Williams coefficients to return stride length (cm and inches), steps per kilometre and steps per mile — useful for calibrating pedometers, smart watches (Apple Watch, Garmin, Fitbit) and treadmills, and for converting a daily 10 000-step target into real distance.

Standing-Desk Daily Calorie-Burn Calculator

Enter body weight and the daily split between standing and sitting; the tool uses MET coefficients (sitting 1.3, standing 1.8) to estimate the extra calories burned per day — handy for weight-loss tracking and ergonomics decisions.

Protein per Meal Distribution Calculator

Enter your daily protein target (g) and meal count (2–6 meals/day); the tool divides the total evenly and compares each meal to the leucine-trigger threshold (25–40 g per meal) — a standard reference for muscle gain, fat-loss muscle retention and post-bariatric nutrition.

HOMA-IR Insulin Resistance Calculator (Matthews 1985)

Enter fasting plasma glucose and fasting insulin. The tool returns HOMA-IR = (FPG × FPI) / 22.5 (SI units) — the standard 1985 Matthews insulin-resistance index — and compares against typical cutoffs (< 1 sensitive / 1–2 average / ≥ 2.5 resistant).

Gestational Age Calculator (from LMP)

Enter the first day of the last menstrual period (LMP) and today's date. The tool uses Naegele's rule to return gestational age in weeks + days, estimated due date (EDD) and trimester — the global obstetric / midwifery standard.

Treadmill Incline → Outdoor-Equivalent Pace Calculator

Enter treadmill speed (km/h or mph) and grade (%). The tool uses the Jones & Doust (1996) + ACSM running-metabolism formula to return the equivalent flat outdoor speed and pace — used to compare treadmill and outdoor training loads.

Daniels VDOT Running Race-Equivalent Calculator

Enter a recent race result (distance + finish time). The tool applies Jack Daniels's VDOT model to predict equivalent finishing times at other distances (5K, 10K, half, full marathon) and lists matching training pace zones.

TyG Index Calculator (Triglyceride-Glucose, insulin-resistance surrogate)

Enter fasting triglycerides (TG) and fasting plasma glucose (FPG); the tool returns the TyG index = ln(TG × FPG / 2) — a surrogate for insulin resistance that needs no insulin assay. Widely used in cardiometabolic risk screening and often more reproducible than HOMA-IR.

Cohen's κ Inter-Rater Agreement Calculator

Enter the 2 × 2 contingency table of two raters scoring the same items (two categories × two raters). The tool returns the observed agreement p_o, expected-by-chance agreement p_e and Cohen's κ = (p_o − p_e) / (1 − p_e), classified using the Landis–Koch scale (slight / fair / moderate / substantial / almost perfect) — a workhorse for medical-diagnosis reproducibility, machine-learning labelling and psychometric studies.

Wells Score for Pulmonary Embolism Calculator

Tick the seven Wells criteria (DVT signs, PE most likely diagnosis, HR > 100, recent surgery/immobilisation, prior DVT/PE, haemoptysis, active cancer); the tool computes the Wells score (0–12.5) and stratifies pulmonary-embolism probability into low / moderate / high (or the dichotomised PE-unlikely / PE-likely groupings) per Wells 1998/2000 — used for emergency-department triage.

CHA₂DS₂-VASc Atrial Fibrillation Stroke Risk Calculator

Enter age and tick the six CHA₂DS₂-VASc comorbidities (CHF, hypertension, diabetes, prior stroke/TIA/thromboembolism, vascular disease, female sex); the tool returns the 0–9 total, the annualised ischaemic-stroke risk (% / year) and the ESC 2020 oral-anticoagulation recommendation.

Centor Score for Strep Pharyngitis Calculator (McIsaac modified)

Tick the four Centor items (tonsillar exudate, anterior cervical adenopathy, fever > 38 °C, absence of cough) and enter age for the McIsaac adjustment; the tool returns the 0–5 total and corresponding group-A streptococcal (GAS) infection probability band (≈1 %, ~10 %, ~17 %, ~35 %, ~50 %) to guide rapid-antigen testing or empirical antibiotics.

ABCD² Score for TIA Stroke Risk Calculator

Enter the five ABCD² items (age ≥ 60, BP ≥ 140/90, clinical features: unilateral weakness +2/speech disturbance +1, duration ≥ 60 min +2/10–59 min +1, diabetes); the tool returns the 0–7 total and the 2-day, 7-day and 90-day post-TIA stroke risk (%).

Glasgow–Blatchford Upper-GI Bleeding Score Calculator

Enter haemoglobin, blood urea, systolic BP, heart rate, sex, and comorbidities (melaena, syncope, liver disease, cardiac failure); the tool returns the 0–23 Glasgow-Blatchford Score (GBS) — the standard ED triage tool for upper-GI bleeding. GBS = 0 identifies very-low-risk patients who can be considered for outpatient follow-up.

PaO₂ / FiO₂ Ratio (P/F Ratio) Calculator — ARDS Severity

Enter arterial oxygen partial pressure PaO₂ (mmHg or kPa) and inspired oxygen fraction FiO₂ (0.21–1.0); the tool returns the P/F ratio and the 2012 Berlin ARDS severity band (mild ≤ 300, moderate ≤ 200, severe ≤ 100).

CURB-65 Community-Acquired Pneumonia Severity Score Calculator

Enter the 5 CURB-65 items (confusion, urea > 7 mmol/L, RR ≥ 30, SBP < 90 or DBP ≤ 60, age ≥ 65); the tool returns the 0–5 score, the matching 30-day mortality band and the corresponding outpatient / inpatient / ICU disposition guidance.

HEART Score for Chest Pain (Risk Stratification) Calculator

Enter history suspicion, ECG findings, age, cardiovascular risk factors and troponin level; the tool returns the 0–10 HEART score and the matching 6-week MACE (major adverse cardiac events) probability — the standard chest-pain triage rule in the emergency department.

qSOFA (Quick SOFA) Sepsis Screening Score Calculator

Tick the three bedside criteria (altered mental status GCS < 15, RR ≥ 22 /min, SBP ≤ 100 mmHg); the tool returns the 0–3 qSOFA score. A score ≥ 2 flags suspected sepsis and higher mortality risk per the Sepsis-3 consensus (JAMA 2016).

CHA₂DS₂-VASc Stroke Risk Score (Atrial Fibrillation)

Tick the eight clinical factors (CHF, hypertension, age ≥ 75 / 65–74, diabetes, stroke / TIA, vascular disease, female sex); the tool returns the 0–9 CHA₂DS₂-VASc score and the matching annual stroke risk — the standard tool for guiding anticoagulation in atrial fibrillation.

NEWS2 (National Early Warning Score 2) Calculator

Enter respiratory rate, SpO₂ (with Scale 2 for hypercapnic respiratory failure), supplemental-oxygen status, systolic BP, pulse, consciousness (ACVPU) and temperature; the tool returns the 0–20 NEWS2 score — the UK Royal College of Physicians 2017 standard adopted across the NHS for early detection of clinical deterioration in adults.

Shock Index (SI) Calculator

Enter heart rate and systolic blood pressure; the tool returns the classic Shock Index (SI = HR ÷ SBP), the Modified Shock Index (HR ÷ MAP), and the Age-adjusted SI (Age × SI) — bedside emergency indicators of occult shock, haemorrhage, and early sepsis.

FIB-4 Liver Fibrosis Index Calculator

Enter age, AST, ALT and platelet count; the tool returns FIB-4 = (Age × AST) ÷ (Platelets × √ALT) — Sterling et al. 2006 non-invasive liver-fibrosis index, widely used to stratify advanced fibrosis risk in chronic HCV, NAFLD and MASLD.

Total Cholesterol to HDL Ratio Calculator

Enter total cholesterol (TC) and HDL cholesterol ("good" cholesterol); the tool returns the TC / HDL ratio with *Framingham Risk Score* risk bands — a more reliable cardiovascular predictor than total cholesterol alone (target < 3.5; > 5 in men, > 4.4 in women is high risk).

Framingham 10-Year Cardiovascular Risk Calculator

Enter age, sex, total cholesterol, HDL, systolic BP (with treatment status), smoking and diabetes; the tool applies the *Framingham 2008 General Cardiovascular Disease* equation (D'Agostino et al., Circulation 2008) to return the 10-year CVD event probability and cardiovascular age — the long-standing risk model behind ATP III, JBS3 and AHA guidance.

Rowing 500m Split & Watts Calculator

Enter a rowing distance and time; the tool converts to your /500m split, average speed and Concept2 power watts = 2.80 ⁄ pace³ — the standard indoor-rowing training metrics.

Baby Blood Type Predictor (ABO + Rh)

Pick both parents' ABO blood group and Rh factor; the tool lists every blood type a child could inherit under Mendelian genetics.

Ponderal Index Calculator

Enter height and weight to compute the Ponderal Index (PI) = mass ÷ height³, a body-size measure that stays more consistent than BMI for very tall, very short or newborn bodies.

Corrected Sodium for Hyperglycemia Calculator

Enter measured sodium and glucose to estimate the true sodium level before hyperglycemia dilutes it.

Calculated Serum Osmolality & Osmolar Gap Calculator

Enter sodium, glucose and urea (BUN) to calculate serum osmolality; supply a measured value to also get the osmolar gap used to screen for toxic alcohol poisoning.

Parkland Formula (Burn Fluid Resuscitation) Calculator

Enter body weight and burn area (%TBSA) to get the 24-hour IV fluid volume from the Parkland formula, split into the first 8 hours and the next 16 hours.

Transferrin Saturation (TSAT) Calculator

Enter serum iron and total iron-binding capacity (TIBC) to compute transferrin saturation (TSAT = iron ÷ TIBC × 100%) for iron-status assessment.

Fractional Excretion of Sodium (FeNa) Calculator

Enter urine and plasma sodium and creatinine to compute the fractional excretion of sodium (FeNa%), used to distinguish prerenal from intrinsic acute kidney injury.

Adjusted Body Weight (ABW) Calculator

Compute ideal body weight (Devine formula) and adjusted body weight from height, actual weight and sex — commonly used for drug dosing in obese patients.

Estimated Blood Volume (Nadler) Calculator

Estimate total blood volume from sex, height and weight using Nadler's equations, plus blood volume per kilogram.

A Body Shape Index (ABSI) Calculator

Compute A Body Shape Index (ABSI) from waist circumference, height and weight (BMI) to gauge health risk linked to central obesity.

Absolute Neutrophil Count (ANC) Calculator

Compute the absolute neutrophil count (ANC) from the total white cell count and the neutrophil percentage (segmented + bands) to grade the severity of neutropenia.

Winter's Formula (Metabolic Acidosis Compensation) Calculator

Use Winter's formula to estimate the expected PaCO₂ from serum bicarbonate (HCO₃⁻) in metabolic acidosis, checking whether respiratory compensation is appropriate.

Bishop Score (Cervical Readiness) Calculator

Score cervical dilation, effacement, station, consistency and position to get the Bishop score, gauging cervical ripeness and the likelihood of a successful labour induction.

Corrected Age Calculator (Premature Baby)

Work out a premature baby's corrected (adjusted) age from the birth date and gestational age at birth, for fairer developmental milestone tracking.

Medication Days' Supply Calculator

Work out how many days a prescription will last (days' supply) from the total quantity dispensed and the daily dose.

Weight-Based Dosage Calculator (mg/kg)

From patient weight and a per-kilogram dose, compute the single and daily drug dose and convert it to millilitres of liquid medicine.

Vitamin IU Converter (IU ⇄ mg / mcg)

Convert International Units (IU) to and from milligrams (mg) / micrograms (mcg) for vitamins A, D, E and C using standard conversion factors.

Calories from Macros Calculator (Protein / Carbs / Fat)

Enter grams of protein, carbs, fat and alcohol to get total calories and the macro percentage breakdown using Atwater factors.

DOTS Powerlifting Score Calculator

Enter bodyweight, sex and total lifted to get your DOTS score — a fair way to compare strength across different bodyweights.

Creatine Dosage Calculator (Loading & Maintenance)

Work out the daily creatine loading and maintenance dose (and per-serving amount) from body weight.

Rockport 1-Mile Walk Test VO₂max Calculator

Estimate VO₂max from your 1-mile walk time, ending heart rate, body weight, age and sex.

SWOLF Swimming Efficiency Score Calculator

Compute your SWOLF score from strokes and seconds per pool length to gauge swimming efficiency (lower is better).

MELD Score Calculator (Liver Disease)

Compute the MELD and MELD-Na score from bilirubin, INR, creatinine and sodium to gauge end-stage liver-disease severity and transplant priority.

Child-Pugh Score Calculator (Cirrhosis)

Compute the Child-Pugh score from bilirubin, albumin, INR, ascites and encephalopathy to grade cirrhosis severity as class A, B or C.

Padua VTE Risk Score Calculator

Assess venous thromboembolism (VTE) risk in hospitalised medical patients with the Padua Prediction Score to guide thromboprophylaxis.

NIHSS (NIH Stroke Scale) Calculator

Score acute stroke severity with the 15-item NIH Stroke Scale, giving a 0–42 total and a severity band.

HAS-BLED Bleeding Risk Score Calculator

Estimate major bleeding risk for atrial-fibrillation patients on anticoagulation with the 0–9 HAS-BLED score.

Wells Score for DVT Calculator

Assess the clinical probability of deep vein thrombosis (DVT) with the Wells prediction score, stratified into low, moderate and high risk.

Ranson Criteria Calculator (Acute Pancreatitis)

Grade acute pancreatitis severity and mortality risk with the Ranson criteria (at admission and 48 hours).

Critical Swim Speed (CSS) Calculator

Work out your critical swim speed (CSS) threshold pace and training zones from a 400 m and 200 m time trial.

GAD-7 Anxiety Screening Calculator

Score anxiety over the past two weeks with the 7-item GAD-7 scale, giving a 0–21 total and a severity band.

PHQ-9 Depression Screening Calculator

Score depression over the past two weeks with the 9-item PHQ-9 questionnaire, giving a 0–27 total and a severity band.

STOP-BANG Sleep Apnea Risk Calculator

Assess obstructive sleep apnea (OSA) risk with the 8-item STOP-BANG questionnaire, giving a 0–8 score and risk band.

Epworth Sleepiness Scale (ESS) Calculator

Rate your chance of dozing in 8 everyday situations to get a 0–24 Epworth daytime-sleepiness score and band.

AUDIT-C Alcohol Screening Calculator

Screen for hazardous drinking with the 3-item AUDIT-C questionnaire, giving a 0–12 score with sex-specific cut-offs.

Blood Alcohol Content (BAC) Calculator

Estimate blood alcohol concentration (BAC) from drinks, body weight, sex and time using the Widmark formula.

Smoking Pack-Years Calculator

Calculate smoking pack-years from cigarettes per day and years smoked to gauge lung-cancer screening risk.

Steps to Calories Calculator

Estimate the calories burned and distance walked from your step count, weight and height.

Mentzer Index Calculator (Anemia Screening)

Compute the Mentzer Index from mean corpuscular volume (MCV) and red-blood-cell count (RBC) to help distinguish iron-deficiency anemia from thalassemia trait.

Reticulocyte Production Index (RPI) Calculator

From reticulocyte percentage, hematocrit and a maturation correction, compute the reticulocyte production index to judge whether the bone marrow is responding adequately to anemia.

Grade-Adjusted Pace Calculator

Convert your running pace to an equivalent flat-ground pace for a given uphill or downhill grade, using the Minetti cost-of-running model.

Maddrey's Discriminant Function Calculator

Compute the Maddrey Discriminant Function (mDF) from prothrombin time and serum bilirubin to gauge severe alcoholic hepatitis prognosis.

BODE Index Calculator (COPD)

Score the BODE index from BMI, airflow obstruction, dyspnoea and exercise capacity to estimate COPD survival prognosis.

Caprini VTE Risk Score Calculator

Use the Caprini score to grade a surgical patient’s venous thromboembolism (VTE) risk and suggested prophylaxis.

Riegel Race Time Predictor

Use one known race result to predict your finish time and pace at another distance (5K, 10K, half, marathon).

Cycling Power-to-Weight (W/kg) Calculator

Divide power in watts by body weight to get W/kg and compare it against a rider-category reference table.

UV Index Safe Sun Exposure Time Calculator

Estimate how long unprotected skin can stay in the sun before burning, based on the UV index and your skin type.

Weightlifting Sinclair Coefficient Calculator

Normalise Olympic weightlifting totals across bodyweights using the official Sinclair coefficient to get a comparable Sinclair Total.

Carbohydrate Loading Calculator

From body weight and loading intensity (g/kg), work out the daily carbohydrate grams and calories to load before an endurance event.

Alveolar–Arterial (A–a) Oxygen Gradient Calculator

Compute the alveolar–arterial oxygen gradient from FiO₂, PaO₂ and PaCO₂, with an age-expected upper limit.

Negative Split Pace Calculator

Plan a negative split from a goal finish time — first-half and second-half times plus per-km or per-mile pace.

Oxygen Tank Duration Calculator

Compute how long a medical oxygen cylinder will last from its gauge pressure, safe residual, cylinder size and flow rate.

Yasso 800s Marathon Time Predictor

Use Bart Yasso's 800m repeats rule to predict your full-marathon finish time and pace from your average 800m interval time.

Alcohol Calories Calculator

Estimate the calories in a drink from its serving size, alcohol content (ABV) and residual carbohydrates.

IPF GL Points Calculator (Powerlifting)

Compute the IPF GL points that let lifters be compared across bodyweight and sex, from bodyweight, sex, event type and total lifted.