About our health & fitness calculators
Fitness and nutrition advice is easy to find and hard to trust. Numbers cut through the noise. A calorie target is a specific number, not a marketing slogan. A protein target for muscle gain is grams per kilogram of bodyweight, not a supplement ad. The Morecalcs health calculators turn evidence-based formulas — Mifflin-St Jeor for BMR, Harris-Benedict activity multipliers for daily calories, waist-to-height and BMI for weight screening, ACOG's 280-day method for pregnancy — into fast, private tools you can use before a workout, at the grocery store, or in a doctor's waiting room.
On this page you'll find every calculator you need to plan and track a healthy body. The BMI calculator gives you a quick screen against clinical categories. The BMR and daily calorie calculators tell you exactly how much energy your body burns at rest and with activity, so you can set a realistic deficit or surplus. The macro calculator splits that calorie target into protein, carbs, and fat based on your goal (fat loss, maintenance, or muscle gain). Body fat and ideal weight tools give you two extra angles on the same question — is my current composition healthy? Pregnancy, ovulation, and due-date calculators support family planning with the same methods obstetricians use. Water intake and calorie-burn tools help you tune the daily habits that everything else depends on.
As with every Morecalcs tool, nothing you enter here is transmitted or stored. Formulas are the ones taught in university nutrition and clinical medicine programs, and each calculator's guide explains exactly which equation is running under the hood — plus when the number should be trusted and when a human clinician's judgment matters more. Use these as a starting point for a conversation with your doctor or coach, not a replacement for one.
Which calculator should I start with?
For weight-management goals, do BMR → daily calories → macros in that order. For general health screening, start with BMI and pair it with the body fat estimator; the two together are far more informative than either alone. For fertility and pregnancy, the due date and ovulation calculators are the essentials.
The formulas we use
BMR uses Mifflin-St Jeor (the most accurate general-population formula). Daily calories multiply BMR by activity level (1.2 sedentary to 1.9 very active). BMI uses the WHO formula. Pregnancy uses LMP + 280 days (Naegele's rule). Body fat uses the U.S. Navy circumference method.
Frequently asked questions
Can I rely on the BMI calculator alone?
BMI is a screen, not a diagnosis. Athletes with a lot of muscle read as overweight, older adults with low muscle can read as normal despite poor composition. Pair BMI with waist circumference for a much better picture.
Is the macro split just an estimate?
The absolute calorie target is precise; the macro split is a starting point. Bodies vary. Adjust protein up if you're training hard, adjust carbs down if you're cutting aggressively.
Are the pregnancy calculators accurate?
They use the same LMP + 280 days method most obstetricians use for initial dating. An ultrasound in the first trimester is more accurate for individual dating.