Harris Benedict Calculator
Compute your basal metabolic rate with the Harris-Benedict equation (1984 Roza-Shizgal revision) from sex, age, weight (lb or kg), and height (inches or cm) — then scale it by activity for daily calories, with a Mifflin-St Jeor comparison.
Example: with Sex Male · Age 30 · Weight 180 · Weight unit lb (pounds) · Height 70 → BMR (Harris-Benedict, revised): 1,865 kcal/day.
- Daily calories (BMR × activity)2,891 kcal/day
- Mifflin-St Jeor BMR, for comparison1,783 kcal/day (82 kcal lower)
Computed by the calculator below using its default values. Change any input to see your own numbers.
Revised Harris-Benedict equations (Roza & Shizgal, 1984). Men: 88.362 + 13.397×kg + 4.799×cm − 5.677×age. Women: 447.593 + 9.247×kg + 3.098×cm − 4.330×age.
A 1919 formula that still gets used
James Harris and Francis Benedict published the original basal-metabolism equations in 1919 from calorimetry on 239 people. In 1984, Roza and Shizgal re-derived the coefficients from a larger dataset — that revised version is what this calculator runs, and what most modern 'Harris-Benedict' tools mean. It predicts resting energy burn from weight, height, age, and sex, then a standard activity multiplier turns BMR into total daily calories.
Because the source population was leaner than today's, Harris-Benedict tends to read 5% or so high for many modern users, which is why the American Dietetic Association's 2005 comparison recommended Mifflin-St Jeor instead. The calculator shows both so you can see the spread — usually 50-150 kcal, smaller than the error in anyone's activity guess.
How it’s calculated
Revised Harris-Benedict (Roza & Shizgal, 1984): men BMR = 88.362 + 13.397×kg + 4.799×cm − 5.677×age; women BMR = 447.593 + 9.247×kg + 3.098×cm − 4.330×age. Daily calories = BMR × activity multiplier (1.2, 1.375, 1.55, 1.725, 1.9). Comparison BMR from Mifflin-St Jeor: 10×kg + 6.25×cm − 5×age + 5 (men) or − 161 (women). 1 lb = 0.45359237 kg; 1 in = 2.54 cm.
Any BMR equation is a population average with real individual scatter of about ±10%, and Harris-Benedict skews high for heavier modern bodies — use it as an educational estimate, not medical advice; clinical nutrition decisions belong with a dietitian or physician.
Harris-Benedict equations, original vs revised
| Equation | Formula (kcal/day) | Example BMR |
|---|---|---|
| Revised 1984, men — used here | 88.362 + 13.397×kg + 4.799×cm − 5.677×age | ≈ 1,865 (man: 30, 180 lb, 5 ft 10 in) |
| Revised 1984, women — used here | 447.593 + 9.247×kg + 3.098×cm − 4.330×age | ≈ 1,387 (woman: 40, 65 kg, 165 cm) |
| Original 1919, men | 66.473 + 13.752×kg + 5.003×cm − 6.755×age | ≈ 1,876 (same man) |
| Original 1919, women | 655.096 + 9.563×kg + 1.850×cm − 4.676×age | ≈ 1,395 (same woman) |
Harris & Benedict, PNAS 1918; Roza & Shizgal, Am J Clin Nutr 1984. Examples computed with the stated coefficients; rounded.
Common mistakes
- Mixing unit systems — entering kilograms with the lb setting understates BMR by hundreds of kcal.
- Applying an activity multiplier and then adding tracker workout calories on top: that double-counts exercise.
- Quoting BMR as 'calories to eat' — BMR is the floor your body burns at complete rest, not an eating target.
- Expecting the original 1919 and revised 1984 coefficients to match other sites exactly; check which version a tool uses before comparing.
Frequently asked questions
What is the Harris-Benedict equation?
The revised (1984) form used here: men BMR = 88.362 + 13.397×kg + 4.799×cm − 5.677×age; women BMR = 447.593 + 9.247×kg + 3.098×cm − 4.330×age. Multiply BMR by 1.2-1.9 depending on activity to estimate total daily calories.
Harris-Benedict or Mifflin-St Jeor — which should I trust?
They usually land within 50-150 kcal of each other. Mifflin-St Jeor tested most accurate in the ADA's 2005 review, so lean on it when they disagree; Harris-Benedict remains popular because decades of plans were built on it.
Is BMR the same as the calories I burn doing nothing all day?
Close but not identical. BMR is measured at complete rest, fasted, in a neutral-temperature room. Even a couch-bound day burns about 20% more than BMR — that is what the 1.2 sedentary multiplier represents.
Why does my result differ from my smartwatch?
Watches use their own equations plus heart-rate adjustments and typically report resting burn a bit differently. Differences of 100-200 kcal are normal; your multi-week weight trend is the only true calibration.
Can I use this to plan a medical diet?
No — it is an educational estimate. Clinical energy needs (illness, pregnancy, eating disorders, significant obesity) are calculated differently and should be set with a registered dietitian or physician.