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Which TDEE formula should you use?

Three equations, three different people, and a simple rule for choosing.

Written by AdnanUpdated 8 min read

Use Mifflin-St Jeor unless you have a reliable body fat measurement. It is the most accurate of the common equations for most adults. If you are very lean or very muscular and know your body fat percentage, Katch-McArdle is usually the better fit. Harris-Benedict is best used as a second opinion. The TDEE calculator runs all three side by side, so you can see the difference for yourself.

The three formulas at a glance

FormulaInputsStrengthWeakness
Mifflin-St Jeor (1990)Weight, height, age, sexMost accurate for most adults in a major reviewAssumes average body composition
Revised Harris-Benedict (1984)Weight, height, age, sexLong track record, widely usedTends to run a little high
Katch-McArdleWeight, body fat %Accounts for muscle directlyOnly as good as your body fat estimate

What the research says

In 2005, Frankenfield and colleagues published a systematic review of the main equations in the Journal of the American Dietetic Association. Mifflin-St Jeor came out as the most reliable: it estimated resting metabolic rate within 10% of the measured value in more non-obese and obese people than the other equations, and it had the narrowest error range. The review also noted gaps: there was less data for older adults and some ethnic groups.

Katch-McArdle takes a different route. Lean tissue such as muscle and organs drives most of your resting energy use, so a formula built on lean mass can follow your body more closely when your composition is far from average.

Three people, three formulas

Here is how the formulas compare for three different people, all calculated with the site's own engine.

PersonMifflin-St JeorHarris-BenedictKatch-McArdle
Sara35, female, 68 kg, 165 cm, 30% fat, light activity1,8911,9751,922
Daniel28, male, 85 kg, 180 cm, 10% fat, very active3,1743,3333,489
Robert45, male, 110 kg, 175 cm, 35% fat, sedentary2,3692,5762,297
  • Sara has fairly average body composition. All three formulas land within about 85 calories, so Mifflin-St Jeor is fine.
  • Daniel is lean and muscular. Katch-McArdle gives him about 315 calories more than Mifflin-St Jeor, because the standard equations don't know how much muscle he carries. If his body fat estimate is good, Katch-McArdle is the better starting point.
  • Robert carries more fat. Katch-McArdle comes in lowest, and Harris-Benedict is about 280 calories above it. Starting from Harris-Benedict could leave him wondering why he isn't losing weight.

How to choose

  1. Don't know your body fat? Use Mifflin-St Jeor.
  2. Know it from a DEXA scan, or careful tape measurements tracked over time? Use Katch-McArdle, especially if you are lean or muscular. You can estimate it with the body fat calculator, then open the Katch-McArdle calculator.
  3. Use Harris-Benedict as a check rather than your main number.

Why we show all three

Seeing the spread tells you how certain your estimate is. If the formulas agree within 100 calories, you can start with confidence. If they are 300 apart, as for Daniel, your body composition matters, and it is worth getting a body fat estimate or testing your number against your scale sooner. Either way, the formula only gets you started. Two to three weeks of real data finishes the job, as explained in how to find your real maintenance calories.

See all three formulas for your own numbers.

Compare formulas

Frequently asked questions

What is the most accurate TDEE formula?
For most healthy adults, Mifflin-St Jeor. A 2005 systematic review found it predicted resting metabolic rate within 10% of measured values in more people than the other equations it tested. If you have a reliable body fat measurement, Katch-McArdle can fit better, especially if you are very lean or muscular.
Why do the formulas give different numbers?
They were built from different groups of people using different methods. Mifflin-St Jeor and Harris-Benedict use weight, height, age and sex. Katch-McArdle uses lean mass only. A gap of 50–200 calories between them is normal.
Is Harris-Benedict outdated?
The original 1919 version is old, and the 1984 revision is still widely used. It tends to give slightly higher results than Mifflin-St Jeor. It is useful as a second opinion rather than a first choice.
Should I average the three formulas?
You can, but it doesn't add much accuracy. It is better to pick the formula that fits you, then correct it with 2–3 weeks of real data from your food log and scale.

Keep reading

Calculate TDEE by handStep by step with a worked example.Katch-McArdle calculatorBMR from lean mass.Body fat calculatorEstimate it with a tape measure.

Sources

  1. 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. PubMed 15883556
  2. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. PubMed 2305711
  3. Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168–182. PubMed 6741850