BMI Calculator
Body Mass Index is the fastest screening number for whether your weight sits in a healthy range for your height. It's what most doctors, gyms, and insurers use as a first checkpoint — enter your height and weight below for an instant reading.
How BMI is calculated
BMI = weight (kg) ÷ height (m)². The CDC treats under 18.5 as underweight, 18.5–24.9 as healthy, 25–29.9 as overweight, and 30+ as obese. BMI doesn't distinguish muscle from fat, so athletes can score high without excess body fat — pair it with the Body Fat % calculator below for a fuller picture.
Calorie Calculator (TDEE)
Your Total Daily Energy Expenditure is how many calories you burn in an average day, activity included. It's the single most useful number for planning weight loss, maintenance, or muscle gain — everything else is just adjusting around it.
How TDEE is calculated
We calculate your BMR using the Mifflin-St Jeor equation, then multiply it by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active). To lose weight, aim for roughly 500 kcal below TDEE per day; to gain, add roughly 300–500 kcal above it.
BMR Calculator
Basal Metabolic Rate is the energy your body burns at complete rest — just to keep your heart, lungs, and cells running. It's the foundation number underneath every calorie and macro plan.
The formula we use
Mifflin-St Jeor: men = 10×weight + 6.25×height − 5×age + 5. Women = 10×weight + 6.25×height − 5×age − 161. It's considered the most accurate equation for the general population today.
Body Fat Percentage Calculator
This uses the U.S. Navy tape-measure method — the same approach used in military fitness assessments — to estimate body fat from a few simple circumference measurements, no calipers required.
About the Navy method
It estimates body density from neck, waist (and hip, for women) circumferences relative to height. It's accurate to within a few percentage points for most body types, though it can be less precise for very lean or very large frames.
Ideal Weight Calculator
Based on the Devine formula — the equation clinicians have used since the 1970s to estimate a healthy target weight for medication dosing and fitness goals alike.
The Devine formula
Men: 50 kg + 2.3 kg for every inch over 5 feet. Women: 45.5 kg + 2.3 kg for every inch over 5 feet. Treat the result as a reference range, not a strict target — frame size and muscle mass shift what's healthy for any individual.
Macro Calculator
Turns your daily calorie target into grams of protein, carbs, and fat — the three numbers that actually decide whether a diet plan works, regardless of the label on it.
Not sure of your calories?
Run the Calorie Calculator above first, then bring that number down here — the macro split adjusts automatically to whichever goal you pick.
Protein Intake Calculator
How much protein you need scales with body weight and activity — someone lifting weights four times a week needs meaningfully more than someone who isn't training at all.
Where these numbers come from
0.8 g/kg is the baseline RDA for sedentary adults. Most sports-nutrition guidance for people training regularly lands between 1.6–2.2 g/kg of body weight per day — going meaningfully higher shows little added benefit.
Water Intake Calculator
A simple daily hydration target based on your body weight and how much you exercise, since sweat losses on training days push your baseline needs up.
How this is estimated
Baseline is 33 ml per kg of body weight, plus roughly 350 ml for every 30 minutes of exercise. Hot climates, pregnancy, and breastfeeding all raise the target further.
Waist-to-Hip Ratio Calculator
Where you carry weight matters as much as how much — waist-to-hip ratio is a WHO-recognized indicator of cardiovascular risk, independent of BMI.
What the ratio means
WHO flags increased health risk above 0.90 for men and 0.85 for women. A lower ratio generally indicates a healthier fat distribution pattern.
Heart Rate Zone Calculator
Your training zones — from easy warm-up to peak effort — calculated from your age using the standard 220-minus-age max heart rate formula.
How zones are set
Max heart rate ≈ 220 − age. Zones are then set as percentages of that max: 50–60% warm-up, 60–70% fat burn, 70–80% cardio, 80–90% peak/anaerobic.
Pregnancy Due Date Calculator
Estimates your due date using Naegele's rule — the standard method obstetricians use, counting 280 days (40 weeks) from the first day of your last period.
About this estimate
This gives an estimated due date only — fewer than 5% of babies actually arrive on the exact calculated day. Your OB may adjust the date after an early ultrasound.
Ovulation Calculator
Estimates your most fertile days based on your last period and typical cycle length — useful whether you're trying to conceive or just tracking your cycle.
How this is estimated
Ovulation typically occurs 14 days before your next period starts. The fertile window spans roughly 5 days before ovulation through the day itself, since sperm can survive that long.
Steps to Calories Calculator
Converts your daily step count into an estimated calorie burn, factoring in your body weight — because the same 10,000 steps burn differently depending on who's walking them.
How this is estimated
Roughly 2,000 steps make up a mile, and each mile burns about 0.53 calories per pound of body weight. This is an average estimate — pace and terrain shift the real number.
Sleep Cycle Calculator
Waking up mid-cycle is why some 8-hour nights still feel groggy. This calculator works backward from your wake-up time in 90-minute cycles to suggest the least disruptive bedtimes.
Why 90 minutes
A full sleep cycle — light sleep, deep sleep, and REM — averages about 90 minutes. Waking at the end of a cycle rather than in the middle of one tends to feel noticeably more refreshing, even with the same total hours.