How to calculate TDEE and BMR

BMR is the calories you’d burn in a coma. TDEE is the calories you burn actually living your life. Both numbers matter, but if you’re trying to lose, gain, or maintain weight, TDEE is the one you eat toward. This guide explains how to calculate both with the Mifflin-St Jeor equation — the current clinical standard — and how to translate TDEE into a calorie target for your actual goal.

BMR vs TDEE — what’s the difference?

BMR (Basal Metabolic Rate) is the energy your body burns just to stay alive: heart beating, lungs breathing, brain running, cells dividing. Lying perfectly still in a dark room at neutral temperature, 24 hours a day. For most adults BMR is between 1,400 and 1,800 kcal/day.

TDEE (Total Daily Energy Expenditure) is BMR plus everything else: walking to the kitchen, typing, digesting food, thermoregulating, and any deliberate exercise. TDEE is typically 1.2–1.9× BMR depending on how active you are.

You don’t eat to BMR. You eat to TDEE, then add or subtract to shift weight.

The Mifflin-St Jeor equation

Adopted as the standard by the Academy of Nutrition and Dietetics in the 1990s after studies showed it beat Harris-Benedict (1919) on accuracy for modern body compositions.

For men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. For women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. Weight in kilograms, height in centimeters, age in years.

A 32-year-old man at 82 kg (180 lbs) and 178 cm (5'10") has a BMR of (10 × 82) + (6.25 × 178) − (5 × 32) + 5 = 820 + 1113 − 160 + 5 = 1,778 kcal. The BMR calculator handles the imperial-to-metric conversion and activity multiplier in one step.

The activity multiplier — and why most people get it wrong

Multiply BMR by the factor that matches your week honestly:

1.2 — sedentary. Desk job, almost no deliberate exercise, walking less than 5,000 steps a day. If you work from home and don’t train, this is you.

1.375 — lightly active. Desk job but walking 5,000– 10,000 steps daily or exercising 1–3 days a week at moderate intensity.

1.55 — moderately active. Exercise 4–5 days a week. Most recreational lifters and runners land here.

1.725 — very active. Daily training, often multiple sessions, or physically demanding job. Construction workers, touring musicians moving gear, military in field training.

1.9 — extra active. Elite endurance athletes in heavy training blocks. Almost nobody reading this qualifies.

The universal mistake is picking a factor one level above reality. Three weekly gym sessions is 1.375, not 1.55. If you pick too high, your calculated TDEE exceeds your real burn, and your “deficit” becomes maintenance. That’s the usual explanation for “I stopped losing weight.”

Turning TDEE into a goal target

A pound of body fat is roughly 3,500 kcal. Split across 7 days, a daily deficit of 500 kcal produces about 1 lb/week of loss. The same math works in reverse for gains.

Cut (fat loss): TDEE − 300 to 500 kcal/day. Aggressive cuts work short-term but hurt training recovery and hormones. 500/day is a sensible ceiling; 300/day is what competitive physique coaches use for preserving muscle.

Maintenance: TDEE ± 100 kcal. This is where body recomposition happens — slow lean-mass gain while fat holds or drops, driven by training and protein, not calorie manipulation.

Lean gain: TDEE + 200 to 300 kcal/day. “Dirty bulks” at +700 kcal/day produce about as much muscle as +250 and three times as much fat. Slow is better.

Protein first, calories second

Hit 0.8–1.0 grams of protein per pound of target body weight before worrying about carb/fat ratios. Protein preserves lean mass in a deficit, is the most satiating macro, and costs more calories to digest than carbs or fat. A 180-lb target means 145–180 g/day — roughly a palm-sized serving of chicken, fish, or Greek yogurt at each meal.

When to recalculate

Every 10 lbs of weight change or every 3 months, whichever hits first. BMR scales with body mass, so dropping 20 lbs means your maintenance calories are ~200 kcal/day lower than when you started. Failing to recalculate is the second most common reason for stalled fat loss (after lying about the activity multiplier).

Use the BMR calculator for the number, the calorie calculator for goal-based targets, and the macro calculator to split TDEE into protein, carbs, and fat once you have a calorie floor.