Calorie Calculator: BMR and TDEE Estimates
Estimate BMR and daily energy expenditure from body measurements and an activity setting. Treat the output as an educational model, not a prescribed intake.
Calorie Calculator (BMR + TDEE) workspace
Calorie estimates are population averages, not medical advice. Individual metabolism varies by body composition, genetics, medications, hormones, and dozens of other factors. For weight-loss, performance, or medical-condition planning, consult a registered dietitian or physician.
Mifflin-St Jeor BMR
Uses the equation the American Dietetic Association recommends — more accurate than the older Harris-Benedict for non-obese adults. Metric and imperial input supported.
Five Activity Levels
Sedentary, light, moderate, very active, extra active — each with a clear definition. Multiplier ranges from 1.2 (desk job) to 1.9 (physical labour + hard training).
Per-Goal Calorie Targets
See the daily calories for each common goal: lose 1 lb / 0.5 lb per week, maintain, gain 0.5 lb / 1 lb per week. Based on the 3,500 kcal ≈ 1 lb fat approximation.
100% Client-Side
Personal stats (weight, height, age, sex) stay entirely in your browser. No upload, no logging, no analytics tied to your numbers.
How this calorie calculator works
Estimate BMR and daily energy expenditure from body measurements and an activity setting. Treat the output as an educational model, not a prescribed intake. Equations estimate energy needs for populations and may not predict an individual's needs accurately. Activity multipliers add further uncertainty. The result does not account for every health condition or life stage; discuss individualized dietary decisions with a qualified health professional.
It uses Mifflin-St Jeor because the Academy of Nutrition and Dietetics (formerly the American Dietetic Association) recommends it as the most reliable prediction equation for healthy adults. The older Harris-Benedict equation from 1919 overstates BMR by 5–10% for modern populations. Cross-check your results with the BMI calculator for a weight-status screen, the body fat calculator for composition, and the water intake calculator for a daily hydration target.
How to use the calorie calculator
- Pick your unit system — metric (kg, cm) or imperial (lb, ft+in); conversion happens automatically.
- Enter your sex, age, weight, and height. These are the only four inputs Mifflin-St Jeor uses.
- Select an activity level honestly — most office workers with a few gym sessions land in “lightly active”, not higher.
- Read BMR first, then TDEE; both update live as you type.
- Scan the five goal rows for daily targets from losing 1 lb/week through gaining 1 lb/week, and start from the one matching your aim.
The exact formula this calculator uses
BMR is calculated with the Mifflin-St Jeor equation (1990). Weight is in kilograms, height in centimetres, and age in years; imperial inputs are converted to metric first (1 lb = 0.45359237 kg, 1 in = 2.54 cm). The only difference between sexes is the final constant.
BMR (men) = 10 · kg + 6.25 · cm − 5 · age + 5
BMR (women) = 10 · kg + 6.25 · cm − 5 · age − 161
TDEE = BMR × activity factor
Goal kcal = TDEE ± (500 per 1 lb/week, 250 per 0.5 lb/week)
- kg — body weight in kilograms
- cm — height in centimetres
- age — age in whole years
- +5 / −161 — the sex constant (men add 5, women subtract 161)
- activity factor — 1.2 (sedentary) to 1.9 (extra active); see the table below
The equation comes from Mifflin MD, St Jeor ST, et al., "A new predictive equation for resting energy expenditure in healthy individuals", American Journal of Clinical Nutrition 1990;51(2):241–247 (PMID 2305711), derived from 498 healthy adults aged 19–78 and validated to within roughly ±10% of indirect-calorimetry measurements.
Worked example: 30-year-old man, 80 kg, 180 cm, moderately active
Plug a 30-year-old man weighing 80 kg at 180 cm, moderately active (×1.55), into the formula step by step:
- 10 · 80 = 800
- 6.25 · 180 = 1,125
- 5 · 30 = 150
- BMR = 800 + 1,125 − 150 + 5 = 1,780 kcal/day
- TDEE = 1,780 × 1.55 = 2,759 kcal/day
- Lose 1 lb/week = 2,759 − 500 = 2,259 kcal/day
- Gain 1 lb/week = 2,759 + 500 = 3,259 kcal/day
Those are the exact numbers the calculator returns for the same inputs: BMR 1,780, TDEE 2,759, with goal targets of 2,259, 2,509, 2,759, 3,009, and 3,259 kcal across the five goals. Numbers are rounded to the nearest whole calorie.
The Five Activity Multipliers, Defined
| Level | Multiplier | Definition |
|---|---|---|
| Sedentary | ×1.2 | Desk job, no formal exercise; under 5,000 steps/day |
| Lightly active | ×1.375 | Light exercise 1–3 days/week; 5,000–7,500 steps/day |
| Moderately active | ×1.55 | Moderate exercise 3–5 days/week; 7,500–10,000 steps/day |
| Very active | ×1.725 | Hard exercise 6–7 days/week; 10,000–12,500 steps/day |
| Extra active | ×1.9 | Physical job + daily training; 12,500+ steps/day |
Most people self-select one bracket too high. Be honest: if you spend 8+ hours seated, your baseline is sedentary regardless of a 45-minute gym session.
Calories per Gram by Macronutrient
| Macro | kcal / gram | Note |
|---|---|---|
| Protein | 4 | Most filling per calorie |
| Carbohydrate | 4 | Includes sugars, starches, fibre |
| Fat | 9 | Most energy-dense; essential for hormones |
| Alcohol | 7 | Often forgotten in daily totals |
| Fibre (subset) | 2 | Partially digested; counted as ~2 kcal/g |
Knowing these conversion factors lets you sanity-check any nutrition label. The big shock for most people: fat at 9 kcal/g is more than twice as calorie-dense as protein or carbs (4 kcal/g). Olive oil isn't bad — one tablespoon is a normal portion — but it's 120 kcal in a portion you can barely see.
Six Calorie-Tracking Mistakes (and Fixes)
1. Eyeballing Portions
Studies show free-pour cooking oil ranges 2–6× the eyeballed amount. Buy a $15 kitchen scale; weigh anything calorie-dense for two weeks until your eye recalibrates.
2. Activity-Level Inflation
Honest defaults: most office workers with 3-4 gym sessions/week are "lightly active", not "moderate". The lower bracket usually fits.
3. Liquid Calorie Blindness
A 16 oz oat-milk latte is 220 kcal. Two per day is a 440-kcal silent surplus — enough to offset an entire daily deficit.
4. Weekend Reset
A 500-kcal weekday deficit + 1000-kcal weekend surplus = net zero. Track Friday-Sunday as carefully as Mon-Thu.
5. Trusting Restaurant Calories
FDA studies show restaurant menu calorie counts vary ±20% from the listed value, almost always in the higher direction. Add a buffer.
6. Aggressive Deficits
Cuts deeper than 25% below TDEE accelerate muscle loss, hormonal drops, and bingeing. 500 kcal/day below TDEE is the sustainable floor for most adults.
The limit no calculator can fix
Mifflin-St Jeor predicts BMR to within roughly ±10% for any individual, which means a calculated 1,780 kcal could be anywhere from about 1,600 to 1,960 in real life. The equation uses only weight, height, age, and sex — it cannot see body composition. Two people at the same weight differ in BMR because muscle burns more at rest than fat, so a lean, muscular person sits at the high end of the range and a higher-body-fat person at the low end.
If you know your body-fat percentage to within ±2% (from a DEXA scan or caliper reading), the Katch-McArdle equation — BMR = 370 + 21.6 · lean mass in kg — is tighter for very lean or very muscular bodies. For everyone else, treat this output as a starting point: track weight and intake for 2–4 weeks, then adjust by 100–200 kcal if the trend is off.
Related health & math calculators
Screen weight status from height & weight
Body Fat CalculatorEstimate body composition for tighter BMR
Water Intake CalculatorDaily hydration target by body weight
Age CalculatorGet exact age, a direct BMR input
Unit ConverterConvert kg ↔ lb and cm ↔ ft
Percentage CalculatorExpress a deficit as a percent of TDEE
GPA CalculatorWeighted-average math, same approach
Tip CalculatorQuick percentage splits at the table
Mortgage CalculatorMonthly payment with amortization
Loan CalculatorPayment, interest & payoff schedule
Compound Interest CalculatorProject savings growth over time
For general informational purposes only — not medical advice. Calorie estimates are population averages and vary by individual. Consult a healthcare provider or registered dietitian before making decisions about weight loss, performance nutrition, or any medical condition.
Last updated: September 15, 2026 · Formula source: Mifflin et al. 1990 (cited above) · Runs 100% in your browser — no uploads, tool input is not sent to Toolk.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the energy your body burns at complete rest; TDEE multiplies it by an activity factor to include all daily movement — from ×1.2 for a desk worker up to ×1.9 for a physical job plus daily training. Use TDEE, not BMR, as your daily calorie reference point.
How accurate is a Mifflin-St Jeor estimate?
Within roughly ±10% of measured metabolism for most healthy adults, so a calculated 1,780 kcal could really be anywhere from about 1,600 to 1,960. Track weight and intake for 2–4 weeks, then adjust by 100–200 kcal if the trend disagrees with the math.
Why subtract 500 calories to lose one pound per week?
A pound of body fat stores roughly 3,500 kcal, and 500 kcal/day over 7 days comes to about that. It is an approximation — real loss includes water and some lean tissue, and metabolism adapts during long deficits — but 500 kcal/day stays the sustainable floor for most adults.
Is my health data sent to a server?
No. Sex, age, weight, height, and activity level are processed locally in your browser, and Toolk's page analytics do not receive any of your calculator inputs. Tool input is not sent to Toolk.
Should I eat different amounts for muscle gain versus fat loss?
Fat loss means TDEE minus 250–500 kcal/day, with the smaller deficit preserving more muscle; lean gain means TDEE plus 250–500 kcal/day alongside 1.6–2.2 g/kg protein and resistance training. Bigger swings mostly add fat, and calories alone cannot decide composition.
Does the calculation account for body composition?
No — Mifflin-St Jeor sees only weight, height, age, and sex, which is why muscular people get underestimates. If you have a DEXA or caliper body-fat reading, the Katch-McArdle equation (370 + 21.6 × lean mass in kg) tracks lean bodies more tightly.
Why am I not losing weight on my calculated intake?
The usual culprits are under-counting intake by 20–30% (cooking oil and drinks especially), overstating your activity bracket, metabolic adaptation of 5–10% during long deficits, or plain genetic variance. Log everything for two weeks before changing anything, then adjust by small steps.