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Health Tools
Free health calculators for BMI, calories, BMR, body fat, pregnancy due date and ovulation.
Free health calculators for BMI, daily calories, BMR, body fat, pregnancy due date and ovulation. Each one uses a published, widely used formula, shows the maths behind your result and runs entirely in your browser, so nothing you type is stored or sent anywhere.
- BMI CalculatorCheck your Body Mass Index on the WHO, Asian and Indian scales, plus a healthy weight for your height.
- Calorie CalculatorFind the calories you burn each day and how much to eat to lose, keep or gain weight.
- BMR CalculatorWork out your Basal Metabolic Rate with the Mifflin-St Jeor and Harris-Benedict formulas.
- Body Fat CalculatorEstimate your body fat percentage from a tape measure, using the US Navy method.
- Pregnancy Due Date CalculatorFind your due date, how many weeks pregnant you are and key pregnancy milestones.
- Ovulation CalculatorSee your fertile window, ovulation day and next period for the next three cycles.
Which calculator do you need?
| If you want to know… | Use | Based on |
|---|---|---|
| Whether your weight is in a healthy range | BMI Calculator | WHO, Asian and Indian guideline categories in one result |
| How much to eat to lose, keep or gain weight | Calorie Calculator | Mifflin-St Jeor equation × activity level, compared with ICMR-NIN 2020 |
| How many calories your body burns at rest | BMR Calculator | Mifflin-St Jeor and revised Harris-Benedict |
| How much of your weight is fat | Body Fat Calculator | US Navy tape-measure method |
| When your baby is due and how far along you are | Pregnancy Due Date Calculator | Naegele’s rule, adjusted for cycle length |
| Your most fertile days | Ovulation Calculator | Cycle length, a 14-day luteal phase and ACOG’s fertile window |
How we build these tools
- Published formulas only. Every calculator names its formula and links to the source, so you can check the maths yourself.
- Private by design. All calculations run on your device. We do not save, send or see your height, weight, dates or results.
- Metric first. Results default to kg and cm, with a switch for pounds, feet and inches.
- Ranges for Indian bodies. The BMI calculator shows the lower Asian cut-offs and the Indian 2009 guideline category next to the global WHO ranges, because South Asians face higher health risks at a lower BMI. The pages also explain where Indian research shows standard equations run high, such as ICMR-NIN’s finding that international BMR equations overestimate Indians by 10% to 12%.
Sources we rely on
Every health claim on these pages links to a primary source. These are the ones we use most:
- World Health Organization (opens in new tab) for global BMI definitions and obesity data.
- ICMR-National Institute of Nutrition (opens in new tab) for the energy needs of Indian adults and pregnant women (2020).
- The 2009 Indian consensus statement (opens in new tab) and the 2025 revised definition of obesity in Asian Indians (opens in new tab), written with doctors from AIIMS New Delhi, for Indian BMI, waist and body fat cut-offs.
- NHS (opens in new tab) for ethnicity-adjusted BMI ranges, safe weight loss and pregnancy scan timings.
- American College of Obstetricians and Gynecologists (ACOG) (opens in new tab) for due dates, the fertile window and fertility checks.
- Peer-reviewed papers for each formula, such as Mifflin and St Jeor (1990) for BMR and Wilcox (1995) for conception timing.
A note on accuracy
These calculators give estimates for healthy adults. They cannot see your medical history, medicines, muscle mass or any condition you may have. Use the results as a starting point for a conversation with your doctor, dietitian or gynaecologist, not as a diagnosis.
FAQ
Health Tools FAQs
Are these health calculators free?
Yes. Every calculator on this page is completely free, with no sign-up and no limit on how many times you use it. They run in your browser, so they also work on slow or patchy mobile connections once the page has loaded.
Is my health data stored anywhere?
No. Your height, weight, measurements and dates never leave your device. The calculations run in your browser and nothing is saved on our servers. The only thing we remember, on your own device, is whether you prefer metric or imperial units.
How accurate are online health calculators?
Online health calculators are as accurate as the formula behind them and the numbers you enter. Equations like Mifflin-St Jeor or the US Navy body fat method are good estimates for most healthy adults, but they can be off for athletes, older adults, pregnant women and people with medical conditions.
Can these calculators replace a doctor?
No. These tools give general estimates, not a diagnosis. They cannot account for your medical history, medicines or test results. If a result worries you, or you plan a big change to your diet, exercise or pregnancy care, talk to a qualified doctor first.
Do these calculators use Indian standards?
Partly. The BMI calculator shows the lower Asian cut-offs, where overweight starts at 23, and your category under the Indian 2009 guideline, which calls 25 or more obese. The calorie page compares your result with ICMR-NIN 2020 energy needs for Indians. The formulas themselves are international, because no Indian-specific equation is built into these tools yet.
Which health calculator should I start with?
Start with the BMI calculator, then measure your waist. If your BMI is above 23 or your waist is 90 cm or more for men or 80 cm or more for women, use the calorie calculator to set a daily target. The BMR and body fat calculators add detail once you have those basics in place.
How often should I recheck my results?
Recheck BMI and calorie targets every 2 to 3 kg of weight change, or about once a month while losing weight. Your calorie needs fall as you get lighter, so an old target slowly stops working. Body fat changes slowly, so once a month is enough. Pregnancy and ovulation dates only need updating when your period or scan dates change.
Can I use these calculators during pregnancy?
Only the due date calculator is designed for pregnancy. BMI, calorie, BMR and body fat results do not apply while you are pregnant or breastfeeding, because your weight, body water and energy needs change. ICMR-NIN advises about 350 kcal a day extra in pregnancy. Ask your gynaecologist about healthy weight gain for you.