Ideal Body Weight Calculator (Devine / Robinson / Miller / Hamwi)

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.