Harris-Benedict Calculator

There are three Harris-Benedict equations, not one

This is the thing most calculators do not tell you. Harris and Benedict published in 1919, from indirect calorimetry on 239 people. Roza and Shizgal re-fitted those data in 1984, adding 98 further subjects, and that revision is what clinical practice generally means by the name. In 2023 Pavlidou and colleagues published a third fit, against 722 adults measured under modern conditions.

So when a site reports a Harris-Benedict figure without saying which version produced it, you cannot check it. This calculator runs all three and labels each one.

The 1984 revision, for men and women

1. M. Men

   BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age)

2. W. Women

   BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age)

The 1919 original

1. M. Men

   BMR = 66.473 + (13.7516 × weight in kg) + (5.0033 × height in cm) − (6.755 × age)

2. W. Women

   BMR = 655.0955 + (9.5634 × weight in kg) + (1.8496 × height in cm) − (4.6756 × age)

The 2023 refit

1. M. Men

   RMR = (9.65 × weight in kg) + (573 × height in m) − (5.08 × age) + 260

2. W. Women

   RMR = (7.38 × weight in kg) + (607 × height in m) − (2.31 × age) + 43

Note the units in the newest one: height enters in metres, not centimetres. Put 175 where it expects 1.75 and the answer is nonsense, which is a good reason to let a calculator do it.

How much do the three versions disagree?

Less than people fear, and in a consistent direction. Across these six bodies the three printings stay within 25 to 102 kcal of each other, and all three run above Mifflin-St Jeor every time.

The pattern worth noticing is the last column. The 1984 revision reads higher than Mifflin-St Jeor for every one of these people, by 54 to 95 kcal, and the 2023 refit by as much as 164. If you have used both and wondered which was broken, neither was: they are two fits to different data, and the gap is the honest uncertainty in predicting resting metabolism from four numbers.

Is Harris-Benedict accurate?

The 1984 reevaluation put it plainly: the equations estimate resting energy expenditure of a normal subject with a precision of about 14%. For a 1,800 kcal result that is roughly 250 kcal either side, before anyone picks an activity multiplier.

That is also why the later refits exist. The 2023 equations were developed against people living under modern conditions, and reported R-squared values of 0.95 for men and 0.86 for women against measured values in their sample, better than the older equations managed on the same data.

Treat any of these as a starting point rather than a measurement. What your maintenance level actually is shows up in the scale over two or three weeks, which maintenance calories explained works through.

Harris-Benedict or Mifflin-St Jeor?

Mifflin-St Jeor is the usual default, and it is what the BMR calculator here runs, because it was derived more recently and tends to sit closer to measured values in modern populations. Harris-Benedict is worth having when you need to match a number produced elsewhere, since plenty of apps, textbooks and clinical tools still use it.

If you want the version that ignores height and uses age bands instead, that is the Schofield equation calculator. To turn any of these resting figures into a full day, the TDEE calculator applies an activity multiplier, and that choice moves the answer far more than the choice of equation does.