Free BMR Calculator — Three Formulas and Your TDEE at a Glance

Every calorie target you’ll ever set starts with one number: your Basal Metabolic Rate — the calories your body burns at complete rest in 24 hours. Eat below it for too long and your body starts breaking down muscle. Eat at your full daily burn and you maintain. The new BMR Calculator gives you that floor, and the daily total built on top of it, in one screen.

BMR is the input; TDEE is the answer

BMR alone doesn’t tell you how much to eat — you’re not in a coma. Your TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor, from 1.2 for desk-bound days to 1.9 for hard physical work. TDEE is the number you actually plan around: eat 300–500 kcal below it to lose fat at the well-studied 0.5–1 lb/week, or above it to gain.

The calculator shows TDEE at all five activity levels side by side. Tap a row to select it and your daily target updates instantly, so you can see exactly what changing your activity does to your budget. For the full breakdown of how the three formulas differ, read BMR vs TDEE, Explained.

Three formulas, one tool

• Mifflin-St Jeor (default) — the modern standard, accurate to within ±10% of measured BMR for most adults.
• Harris-Benedict (revised) — the older equation, useful when you want to match a legacy app or textbook.
• Katch-McArdle — the most accurate of the three if you have a real body-fat percentage, because it works from lean body mass directly. Pick it without entering body fat and the tool gently falls back to Mifflin and tells you why.

Metric and imperial are both built in (lb → kg, ft+in → cm), and lean body mass is shown whenever Katch-McArdle is active.

Free, and it stays free

Open any popular diet app — MyFitnessPal Premium runs $19.99/mo, Cronometer Gold around $4.99–10.99/mo — and you’ll find this exact calculation hidden inside a paid goal-setup flow. Here it’s the whole point of the page, free, with nothing sent to a server. A future Pro tier could add saved profiles, a TDEE history chart, and a multi-client roster for trainers, but the calculator itself on the tool page will always be free.

A note of caution: this is an informational estimate, not medical advice. Real metabolism varies with genetics, thyroid function, and dieting history. Treat the number as a good starting point, adjust ±200 kcal based on how your weight actually tracks over 2–4 weeks, and consult a professional before big dietary changes.

Frequently Asked Questions

Which BMR formula should I use? Mifflin-St Jeor for most adults — it is the Academy of Nutrition and Dietetics’ recommendation. Use Katch-McArdle if you have a real body-fat measurement.

Is BMR the same as TDEE? No. BMR is calories burned at complete rest; TDEE is BMR multiplied by an activity factor (1.2 to 1.9). TDEE is the number you use for calorie targets.

Is this medical advice? No. It is an informational estimate. Talk to a doctor or registered dietitian before making significant changes to your diet.

Try it now — Open the BMR Calculator — no signup required.