BMR and TDEE Calculator — How Many Calories Does Your Body Actually Need?

If you've ever tracked calories and wondered why the number on every app seems slightly different, the answer usually comes down to which BMR formula they're using and how they estimate your activity level. Let's unpack both.

The BMR & TDEE calculator on CalcHub runs the math for you — but knowing what's happening behind the scenes makes the result actually useful.

BMR vs. TDEE — What's the Difference?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive. Breathing, circulation, cell repair. Nothing else. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor. It's the real-world number: how many calories you burn on a typical day when you factor in walking, working out, fidgeting, and everything else.

Most people dramatically underestimate their TDEE, which is why "eating less" often feels unsustainable — they're cutting from a number that was already too low.

How to Use the Calculator

1. Enter your age, sex, height, and weight
2. Select your activity level (see table below)
3. The calculator returns your BMR and TDEE

Use your TDEE as the baseline for any diet or fitness goal — not your BMR.

Activity Level Multipliers

Activity Level	Description	Multiplier
Sedentary	Desk job, little to no exercise	BMR × 1.2
Lightly active	Light exercise 1–3 days/week	BMR × 1.375
Moderately active	Moderate exercise 3–5 days/week	BMR × 1.55
Very active	Hard exercise 6–7 days/week	BMR × 1.725
Extremely active	Physical job + daily training	BMR × 1.9

Most people who exercise a few times a week land in "moderately active." Be honest here — overestimating your activity is the number one reason people stall on fat loss.

Which Formula Does CalcHub Use?

The CalcHub calculator uses the Mifflin-St Jeor equation, which is generally considered the most accurate for the general population:

• Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
• Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

The older Harris-Benedict formula still circulates widely but tends to slightly overestimate calorie needs.

Using TDEE for Your Goals

Once you have your TDEE:

• Fat loss: Eat 300–500 calories below TDEE (a 500-calorie deficit = roughly 1 lb/week loss)
• Maintenance: Eat at TDEE
• Muscle gain: Eat 200–300 calories above TDEE (a lean bulk)

Aggressive deficits beyond 1,000 calories/day tend to backfire — muscle loss increases, hunger becomes unmanageable, and metabolic adaptation kicks in. These are estimates. Individual metabolism varies significantly. Consult a registered dietitian for personalized guidance.

Why does my TDEE seem too high?

Activity multipliers are averages, and calorie tracking tools often overestimate burn during exercise. If you're not losing weight at a deficit based on your TDEE, try reducing calories by another 100–150 before assuming the formula is wrong.

Does metabolism slow down with age?

Yes, but less dramatically than most people think. BMR typically decreases by around 1–2% per decade after age 20. More impactful is the gradual muscle mass loss that happens with age — muscle burns more calories at rest than fat does.

Should I recalculate my TDEE after losing weight?

Yes. As your weight changes, your BMR changes with it. Recalculate every 10–15 lbs to keep your targets accurate.

Related Calculators

• Calorie Calculator — calories by goal and food type
• Macro Calculator — split those calories into protein, carbs, fat
• Ideal Weight Calculator — find your target weight