TDEE basics · 7 min read
How to Calculate Your TDEE by Hand (Step-by-Step, With Real Examples)
Every TDEE calculator on the internet — including ours — runs on a couple of published equations that you can work through with nothing more than a pen and your phone's calculator. Doing it by hand once is worth ten minutes of your time: you'll understand exactly where your number comes from, why two calculators can disagree by a few hundred calories, and how to adjust the estimate when real life doesn't match the prediction.
TDEE stands for Total Daily Energy Expenditure — the total calories your body burns per day. The hand calculation has three steps: estimate your BMR (the energy you'd burn at complete rest), multiply it by an activity factor, then sanity-check the result against the real world. Let's do all three.
What you need before you start
- Body weight in kilograms (pounds ÷ 2.2046)
- Height in centimetres (inches × 2.54)
- Age and sex
- Optional but valuable: a body-fat estimate — it unlocks the second, often more accurate formula. If you don't know yours, our body-fat calculator estimates it from tape measurements.
Step 1 — Estimate your BMR with Mifflin-St Jeor
The Mifflin-St Jeor equation, published in 1990 in the American Journal of Clinical Nutrition, is the default in most serious calculators for a good reason: when the American Dietetic Association compared the popular prediction equations against measured resting metabolic rates, Mifflin-St Jeor was the most reliable across both normal-weight and obese adults.
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161
Worked example — Maria, 34, 65 kg, 165 cm:
10×65 = 650 | 6.25×165 = 1,031 | 5×34 = 170
BMR = 650 + 1,031 − 170 − 161 = ≈ 1,350 kcal/day
That 1,350 kcal is what Maria's body would burn lying still for 24 hours — keeping her heart, brain, liver and the rest of the machinery running. It is not an eating target; it's the foundation we build on.
Step 1, alternative — Katch-McArdle if you know your body fat
Mifflin-St Jeor only sees your total weight — it can't tell muscle from fat. Muscle tissue burns considerably more energy at rest than fat tissue, so for people who are leaner or heavier-set than average, a formula built on lean body mass does better:
BMR = 370 + 21.6 × LBM
Worked example — David, 28, 82 kg, 180 cm, 18% body fat:
LBM = 82 × 0.82 = 67.2 kg → BMR = 370 + 21.6×67.2 = ≈ 1,822 kcal/day
Mifflin-St Jeor for David: 820 + 1,125 − 140 + 5 = ≈ 1,810 kcal/day
For David the two formulas land 12 kcal apart — at average body composition they converge, and either is fine. They diverge at the extremes: a 90 kg athlete at 8% body fat gets ≈ 1,880 kcal from Mifflin-St Jeor but ≈ 2,158 kcal from Katch-McArdle — a 280 kcal gap, because the weight-only formula can't see all that muscle. This is exactly why our calculator switches to Katch-McArdle automatically whenever you provide a body-fat estimate.
Step 2 — Multiply by an honest activity factor
Your BMR covers lying still. Everything else — walking, training, working, fidgeting, digesting — gets bundled into one multiplier:
| Activity level | Factor | Typical week |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise 1–3 days/week |
| Moderately active | 1.55 | Moderate exercise 3–5 days/week |
| Very active | 1.725 | Hard exercise 6–7 days/week |
| Athlete | 1.9 | Twice-daily training or a physical job |
This is where most hand calculations (and calculator inputs) go wrong. People grade their most active week, not their average one. A useful reality check: if you train hard four days a week but spend the other ~65 waking hours sitting, you are probably a 1.55, not a 1.725. When torn between two levels, pick the lower one — it's easier to add calories later than to explain a stalled fat-loss phase.
Maria (light exercise 2×/week): 1,350 × 1.375 = ≈ 1,856 kcal/day
David (lifts 4×/week, desk job): 1,822 × 1.55 = ≈ 2,824 kcal/day
Step 3 — Verify against reality (the step everyone skips)
Even the best prediction equations carry roughly ±10% error for an individual — for David that's a ±280 kcal window. The fix isn't a better formula; it's two weeks of data:
- Eat normally and log everything honestly for 14 days.
- Weigh yourself every morning under the same conditions; compare the weekly averages (daily readings bounce around with water and food in transit — averages don't lie).
- If your average weight held steady, your average intake was your TDEE — more accurate than any formula. If you lost or gained, each kilogram of change represents roughly 7,700 kcal of cumulative deficit or surplus; divide by 14 days to adjust your estimate.
Formula first, reality second. The equation gives you a starting point in minutes; the logbook turns it into your number.
The four most common mistakes
- Double-counting exercise. If your activity multiplier already includes your training, don't also "eat back" the calories your watch says you burned. Pick one accounting system.
- Aspirational activity levels. Grade the week you actually live, not the one in your training plan.
- Treating TDEE as fixed. It scales with your body weight and adapts during long diets — recalculate after every 4–5 kg of change.
- Expecting daily precision. TDEE is a weekly average concept. Judge progress on weekly averages, never on yesterday.
Prefer to skip the arithmetic?
The free calculator runs both formulas (and picks the right one for your inputs), then turns the result into calorie and macro targets for cutting, maintaining or bulking.
Open the TDEE & Macro Calculator →Frequently asked questions
Which formula is more accurate, Mifflin-St Jeor or Katch-McArdle?
For most people they land within 1–2% of each other. Mifflin-St Jeor is the best-validated weight-based equation and the safer default when you don't know your body fat. Katch-McArdle pulls ahead for noticeably lean or noticeably heavier-set people, because it works from lean mass instead of total weight.
How often should I recalculate?
After every 4–5 kg (≈ 10 lb) of weight change, or whenever your routine shifts meaningfully — new job, new training schedule, injury. TDEE is a moving target, not a constant.
Why do different calculators give different numbers?
Different BMR equations, slightly different multipliers attached to the same labels, and sometimes hidden adjustments. A 100–300 kcal spread between tools is normal. Treat any of them as a starting estimate and let two weeks of logging settle the argument.
Is my BMR the number of calories I should eat?
No — BMR is a component of TDEE, not an eating target. Targets are set relative to TDEE: at it to maintain, below it to cut, slightly above it to gain. Long stretches at or below BMR are unnecessarily aggressive for most people.
References
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi:10.1093/ajcn/51.2.241
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789. doi:10.1016/j.jada.2005.02.005
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Lippincott Williams & Wilkins (8th ed.) — source of the Katch-McArdle resting metabolism equation.