Mifflin-St Jeor vs Harris-Benedict: Which Calorie Formula Is More Accurate

Search for a calorie calculator and you’ll run into two formula names: Harris-Benedict and Mifflin-St Jeor. They estimate the same thing, your Basal Metabolic Rate, but they were built more than 70 years apart using very different data, and that gap actually matters.

The Harris-Benedict formula (1919, revised 1984)

Originally published in 1919 and revised in 1984, Harris-Benedict was the standard BMR formula for most of the 20th century:

• Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
• Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)

The Mifflin-St Jeor formula (1990)

Published in 1990 using a larger, more contemporary sample of subjects, Mifflin-St Jeor was developed specifically because researchers found Harris-Benedict was overestimating BMR for the modern population:

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

Side-by-side comparison

For a 30-year-old man, 170 cm tall, weighing 70 kg (the same profile used in our calorie calculator example):

Formula	Calculated BMR
Mifflin-St Jeor	≈ 1,618 calories/day
Harris-Benedict (revised)	≈ 1,672 calories/day

Harris-Benedict comes in about 54 calories higher for this profile. That gap tends to widen further for people who are overweight, since Harris-Benedict was built on a leaner, less representative population than today’s.

Which one should you actually use

The Academy of Nutrition and Dietetics recommends Mifflin-St Jeor as the more accurate formula for the general population, which is why it’s the formula built into our calorie calculator. Harris-Benedict isn’t wrong, just less precisely calibrated to today’s population than the formula that replaced it.

Either formula is still just an estimate. Individual metabolism varies by roughly 10-15% between people with identical stats, so treat the result as a starting point to adjust from based on your own real-world progress, not a fixed, precise number.

Why do BMR calculators give different results depending on the formula used?

Each formula was built from a different research sample at a different time. Mifflin-St Jeor used more recent, representative data and is generally considered more accurate for most people today.

Is Harris-Benedict outdated?

It’s not wrong, but it tends to overestimate BMR compared to Mifflin-St Jeor, particularly for people who are overweight, since the original research population wasn’t representative of today’s broader population.

Which formula do most dietitians recommend?

The Academy of Nutrition and Dietetics recommends Mifflin-St Jeor as the more accurate equation for estimating BMR in healthy adults.

How accurate is any BMR formula?

Both formulas are estimates. Actual metabolism varies between individuals by roughly 10-15% even with identical height, weight, and age, so use the result as a starting point and adjust based on real-world results over a few weeks.