Health & Fitness Calculators

What the health and fitness calculators cover

Sixteen calculators for the numbers people want before changing how they eat or train: daily energy needs, body composition, training targets, pregnancy timing, and a few everyday health measures. All free, no account, and no data leaves your browser. They are educational estimates, not medical advice — a doctor or dietitian should guide anything that matters clinically.

Energy, weight, and macros

• TDEE — total daily energy expenditure including activity, adjusted for losing, maintaining, or gaining.
• BMR — the calories your body burns at rest, using Mifflin–St Jeor or Harris–Benedict.
• Macro calculator — split a calorie target into protein, fat, and carbohydrate grams.
• BMI — body mass index with a visual gauge against the WHO categories.

Body composition

• Body fat — estimate body-fat percentage, plus fat mass and lean body mass, from simple measurements.
• Waist-to-hip ratio — where you carry fat, which BMI cannot tell you.

Training and performance

• Heart-rate zones — training zones from the Karvonen method using your resting and maximum heart rate.
• Running pace — pace, speed, and finish time for a distance.
• One-rep max — estimate your 1RM from a set you have actually lifted.

Pregnancy and cycle

• Pregnancy due date — an estimated due date from your last menstrual period.
• Ovulation — the likely fertile window within a cycle.
• Pregnancy weight gain — the recommended gain range by starting BMI.

Everyday health

• Water intake — a daily fluid target from body weight and activity.
• Sleep cycle — bedtimes and wake times aligned to 90-minute sleep cycles.
• BAC estimator — a rough blood-alcohol estimate for education, never for deciding whether to drive.

TDEE, BMR, BMI, macros — what is the difference?

BMR is your resting calorie floor. TDEE is BMR plus everything you do — the number that actually drives weight change. BMI is a height-to-weight ratio that screens body size but ignores composition. Macros are the breakdown of your calories into protein, fat, and carbohydrate. The usual order is BMR for the baseline, TDEE for the target, macros to plan meals, and BMI or body fat for context. The figure that matters most for weight is TDEE, because nothing changes until intake moves relative to it.

How to use the results together

1. Estimate BMR, then multiply by activity to reach TDEE. Treat TDEE as maintenance calories.
2. For fat loss, eat roughly 500 kcal below TDEE; for muscle gain, about 300 above. Keep protein high either way.
3. Turn the target into grams with the macro calculator, and anchor protein first.
4. Use body-fat or waist-to-hip measurements to track composition, since the scale alone cannot tell muscle from fat.
5. Adjust every 5–10 lbs of change, because a lighter body burns fewer calories.

Common mistakes

• Eating to BMR instead of TDEE. BMR is a resting floor; eating exactly to it is usually a steeper deficit than intended.
• Overrating activity. Choosing “very active” when you train twice a week inflates TDEE and slows progress.
• Trusting BMI alone. Muscular people can read as “overweight” while lean; add a body-fat or waist measure.
• Judging by daily weight. Water and glycogen move body weight several pounds a day; compare weekly averages.
• Treating estimates as diagnosis. These tools do not detect conditions and should not replace clinical assessment.

Frequently asked questions

Are these calculators medical advice?

No. They produce educational estimates from published formulas. Pregnancy timing, alcohol, diet, and training decisions that carry risk should be discussed with a healthcare professional.

How accurate are the body-composition estimates?

Reasonable for tracking change over time, less reliable as a one-off absolute. Methods based on measurements or formulas carry real error, so use the same method repeatedly and watch the trend rather than a single reading.

Can I use these if I am pregnant or have a medical condition?

Some, with care. Calorie and weight targets change during pregnancy, and generic formulas may not apply. The pregnancy-specific tools are a better starting point, and a clinician should set the actual targets.

If a health goal has a budget attached — a gym membership, a meal plan, equipment — the finance calculators handle the money side of the same plan.