Free Health Calculators
These health calculators turn the numbers you already know — height, weight, age and activity — into the figures nutrition and health guidance is built on: body mass index, resting energy use, daily calories and a macro split. Each one works in metric or imperial units, shows the formula it uses and lists its limits, because a single number can never describe your health. Use them to get oriented, then take real questions to a doctor or registered dietitian.
Weight and energy
Start here to see where you are and how much energy your body uses.
BMI CalculatorCalculate body mass index for adults in kg/cm or lb/feet/inches, with the WHO category and the healthy weight range for your height.
Calorie Calculator (TDEE, BMR & Macros)Estimate your BMR, daily calorie needs (TDEE), a calorie target for your goal and a macro split, in lb/ft or kg/cm.
Body Fat Calculator (US Navy Method)Estimate body fat percentage from height, neck, waist (and hip) measurements in cm or inches using the US Navy method.Sleep, caffeine and fitness
Track sleep debt and caffeine, and plan strength training weights.
Sleep Debt CalculatorAdd up how much sleep you owe from the past week and estimate how many nights of extra sleep it takes to recover.
Caffeine CalculatorAdd up your daily caffeine from coffee, tea, soda and energy drinks, compare it with the 400 mg guidance and see how much is left at bedtime.
One Rep Max CalculatorEstimate your one-rep max (1RM) from any set using six formulas, with a training-weight table by percentage.Pregnancy and fertility dates
Estimate a due date, ovulation and the fertile window, and work back to conception.
Pregnancy Due Date CalculatorEstimate your due date from your last period, conception date or IVF transfer, with your week of pregnancy and key milestones.
Ovulation CalculatorEstimate your ovulation day, fertile window and next period from your cycle, with the next three cycles mapped out.
Conception Date CalculatorWork out when you probably conceived from your due date or last period, with the likely conception window.Units and everyday maths for health tracking
Convert between kilograms and pounds, centimetres and feet, and work out percentage changes in weight.
Weight ConverterConvert kilograms, pounds, ounces, stone, grams and tonnes quickly and exactly.
Length ConverterConvert metres, kilometres, centimetres, miles, yards, feet and inches instantly.
Percentage CalculatorFind a percent of a number, percent change, and increases or decreases.
Age CalculatorWork out exact age in years, months and days, plus the days until your next birthday.Which health calculator should I use?
Use the BMI calculator for a quick screening of weight against height and to see the weight range that counts as healthy for your height. Use the calorie calculator when the question is about food: it estimates your basal metabolic rate (BMR), your total daily energy expenditure (TDEE) and a daily target for losing, maintaining or gaining weight, with protein, carbohydrate and fat in grams.
The two answer different questions. BMI describes a snapshot of your size; the calorie calculator estimates energy flow. Many people use both: BMI to see whether a change might be worthwhile, calories to plan one.
How accurate are health calculators?
They are population averages. The BMI formula can’t tell muscle from fat, and BMR equations such as Mifflin–St Jeor predict resting energy within roughly ten percent for most adults but can miss for any individual. Treat every result as a starting hypothesis: change one thing, watch your real-world trend for two to three weeks, then adjust.
Every health page on this site shows its formula, cites primary sources (WHO, NHS, NIH) and carries a visible disclaimer, a last-reviewed date and a link to our editorial policy.
Related reading
Not sure which number to track? Read BMI, body fat or calories: which number should you track?
More on sleep, caffeine and lifting
When to see a professional
- You are pregnant or breastfeeding, or under 18 — standard adult formulas do not apply.
- You have diabetes, thyroid disease, kidney disease or another condition affecting weight or diet.
- You are thinking of eating well below the calorie floors the calculator applies (1,200 kcal for women, 1,500 kcal for men).
- Changes in weight are unexplained or you are worried about your relationship with food.
Guides for this topic
How to Calculate BMI6 min readHow to Calculate TDEE and Daily Calories7 min readHow to Calculate Body Fat Percentage6 min readHow to Calculate Your Pregnancy Due Date7 min readHow to Calculate Sleep Debt6 min readHow Much Caffeine Is Too Much?6 min readHow to Calculate Your One-Rep Max7 min readFrequently asked questions
Are these health calculators medical advice?
No. They are educational tools using standard published formulas. They cannot diagnose or treat anything; talk to a healthcare professional about your own situation.
Do the calculators work in pounds and feet?
Yes. Choose imperial units on any health calculator and enter feet and inches for height.
Is my data stored?
No. Everything is calculated in your browser. Nothing you type is sent to a server. Only if you press a share button does the page build a link containing your inputs, and only you decide where to send it.
Where do the formulas come from?
BMI categories follow the World Health Organization’s adult ranges. Calorie estimates use the Mifflin–St Jeor (1990) and revised Harris–Benedict equations. Each tool page lists its sources.
Reviewed September 26, 2026 by the SolveCalcPro editorial team. See our editorial policy. All tools →