9 free tools · run in your browser
Free health calculators
Quick, private estimates for weight, energy, sleep, cycles and training. Every number is worked out in your browser, and each page explains its formula.
Health calculators
- BMI calculatorCheck your BMI, the healthy weight range for your height and your waist-to-height ratio.
- Calorie calculatorWork out daily calories to lose, maintain or gain weight, and split them into protein, carb and fat targets per meal.
- TDEE calculatorEstimate daily calories, BMR and macros with the Mifflin-St Jeor formula.
- Body fat calculatorEstimate adult body fat using circumference or a BMI-based equation.
- Ideal weight calculatorCompare Devine, Robinson, Miller and Hamwi formula estimates.
- Sleep calculatorFind bedtimes and wake-up times that line up with 90-minute sleep cycles.
- Due date calculatorEstimate a due date from LMP, conception, or ultrasound gestational age.
- Period calculatorEstimate upcoming periods and a possible fertile window from cycle length.
- Pace calculatorCalculate pace, distance or finish time with kilometre or mile splits.
Which calculator answers your question?
- Is my weight in a healthy range? The BMI Calculator gives your BMI, the healthy weight range for your height and, if you add your waist, your waist-to-height ratio.
- How much body fat do I have? The Body Fat Calculator uses the US Navy tape-measure method or a BMI-and-age estimate.
- What should I weigh? The Ideal Weight Calculator compares the Devine, Robinson, Miller and Hamwi formulas with the healthy BMI range.
- How many calories do I burn? The TDEE Calculator estimates your BMR and daily energy use with the Mifflin-St Jeor equation.
- How much should I eat to lose or gain? The Calorie & Macro Calculator sets a calorie target and splits it into protein, carbs and fat.
- When should I go to bed? The Sleep Calculator lines bedtimes and alarms up with 90-minute sleep cycles.
- When is my baby due, or my next period? Use the Due Date Calculator or the Period Calculator.
- What pace do I need for a race time? The Running Pace Calculator works out pace, time or distance, with splits.
Estimates, not diagnoses
Each of these tools uses a published, population-level formula: BMI is weight divided by height squared, TDEE uses Mifflin-St Jeor, body fat uses the US Navy equations, and the standard due date is 280 days after the first day of your last period. Formulas like these describe averages well and individuals less well. Two people with the same BMI can carry very different amounts of muscle and fat, and a calorie estimate can be a few hundred calories off for you.
Use the results as a starting point, watch how your body actually responds, and look at more than one measure. Our guide what is a healthy BMI, and what are its limits? explains where BMI works and where it doesn't. None of these calculators is medical advice. If a result worries you, or you're pregnant, have a health condition or are under 18, talk to a doctor.
Private by design
Health numbers are personal. Every calculator here runs entirely in your browser: there's no account, and your height, weight, dates and measurements aren't uploaded or stored on a server.
Guides
Frequently asked questions
What is a healthy BMI?+
For adults, a BMI of 18.5 to 24.9 is classed as a healthy weight, 25 to 29.9 as overweight and 30 or more as obese. Lower cut-offs are often used for people of Asian descent. Check yours with the BMI Calculator.
What's the difference between BMR and TDEE?+
BMR (basal metabolic rate) is the energy your body uses at complete rest. TDEE (total daily energy expenditure) is BMR multiplied by an activity factor, so it covers everything you do in a day. Eating around your TDEE keeps your weight roughly stable.
How accurate is the US Navy body fat method?+
It's a reasonable estimate from a tape measure, but individual results can be several percentage points off. Measure at the same spots and time of day, and watch the trend rather than any single reading.
Is BMI accurate for athletes?+
Not very. BMI can't tell muscle from fat, so muscular people often score as overweight. Waist-to-height ratio or a body fat estimate gives a better picture.
How is a due date calculated?+
The standard method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last menstrual period. An early ultrasound scan is more accurate, and only a small share of babies arrive on their due date.
Why does the sleep calculator use 90-minute cycles?+
Sleep runs in cycles of roughly 90 minutes, and waking at the end of one tends to feel easier than waking mid-cycle. Cycle length varies from person to person, so treat the times as a guide.
Are my health details saved?+
No. The calculations run in your browser and nothing you enter is sent to us or stored on a server.