BMR vs TDEE: the two numbers behind every calorie plan
Every calorie target starts with two figures.
Your basal metabolic rate (BMR) is what your body burns at complete rest to keep you alive — heartbeat, breathing, brain activity and cell repair — and it typically accounts for 60–70% of everything you burn in a day.
Our BMR Calculator estimates it with the Mifflin-St Jeor equation, the formula clinicians and dietitians default to because it predicts resting energy more accurately than the older Harris-Benedict method.
For men it is 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women the final constant is −161.
Your total daily energy expenditure (TDEE) then multiplies BMR by an activity factor, from 1.2 for sedentary up to 1.9 for a physical job plus hard training.
The TDEE Calculator does that step and shows the number you eat to hold your weight — the anchor for losing, maintaining or gaining.
Chaining the tools: from calories to macros and body composition
These calculators are built to work in sequence. Start with BMR, layer on activity for TDEE, then feed that maintenance figure into the Macro Calculator, which splits any calorie target into grams of protein, carbohydrate and fat.
The arithmetic is simple: protein and carbs supply about 4 calories per gram and fat about 9, so a 30/40/30 split divides calories by percentage and then by 4 or 9 to reach gram targets.
To track composition rather than just weight, the Body Fat Calculator uses the US Navy circumference method — neck and waist for men, plus hip for women, measured against height —
to estimate body fat within roughly 3–4% of a lab scan.
The Ideal Weight Calculator pairs the Devine formula with the healthy-BMI range (18.5–24.9), and the One Rep Max Calculator averages the Epley and Brzycki formulas to estimate strength from a set you can already lift.
Important: these are planning estimates, not medical advice
Every tool here uses standard, published formulas and the figures you type in, so each result is a well-founded estimate — not a diagnosis or a personalised health assessment.
Equations like Mifflin-St Jeor, the US Navy method and the Devine formula are built on population averages, so your real numbers depend on muscle mass, genetics, hormones, medications and dieting history.
Treat the outputs as a starting budget: set a calorie or macro target, track your weight and measurements for two to three weeks, and adjust based on what actually happens rather than the prediction alone.
Body-fat and BMI figures are screening estimates, not clinical body-composition scans. Do not use these calculators to guide decisions about a medical condition, medication dosing, an eating disorder, pregnancy or any health concern.
For those, consult a doctor, registered dietitian or qualified coach who can assess your individual circumstances.