RMR Calculator | Predicted Resting Energy
Calculate Mifflin–St Jeor REE for ages 19–78 and compare the existing revised Harris–Benedict prediction.
Disclaimer: For informational purposes only. Not a substitute for professional medical advice. Always consult a healthcare provider for health-related decisions.
RMR Calculator – Resting Metabolic Rate
Table of Contents
What is resting energy expenditure?
Basal measurement uses controlled resting and post-absorptive conditions. Resting-energy prediction instead substitutes inputs into a regression equation. FAO/WHO/UNU definitions distinguish basal conditions and total expenditure. This form does not perform calorimetry.
Total daily expenditure includes energy beyond rest. A selected numerical product is not a measurement of that expenditure, a minimum food allowance, or a verified maintenance intake. There is no fixed percentage gap between the displayed equations.
Named prediction methods
Mifflin–St Jeor (February 1990): men: REE = 10 × W + 6.25 × H − 5 × A + 5; women: REE = 10 × W + 6.25 × H − 5 × A − 161. W is kg, H is cm and A is years; output is kcal/day. Original paper, simplified equations.
The study included 498 healthy adults aged 19–78, including normal-weight and obese participants. This tool restricts Mifflin illustrations to 19–78; that range is not a guarantee of personal accuracy.
Revised Harris–Benedict (Roza–Shizgal, July 1984): men: REE = 88.362 + 13.397 × W + 4.799 × H − 5.677 × A; women: REE = 447.593 + 9.247 × W + 3.098 × H − 4.330 × A. W is kg, H is cm and A is years; output is kcal/day. Original paper, Table 3, equations 3 and 6.
Inputs and evidence limits
Enter weight, height and age in the displayed units, then select the male or female coefficient set used in the source. These labels identify equation coefficients, not a measurement of body composition. Inputs must be complete finite numbers; results are cleared when contributing inputs change.
Metric inputs use kg and cm. Where imperial choices are present, pounds are multiplied by 0.45359237 and inches by 2.54 before calculation. Displayed kcal/day is rounded to a whole number.
The model uses the entered weight, height and age; it does not measure lean mass, physical activity, thyroid function or illness. Its arithmetic acceptance checks are not a medical assessment.
Predicted equations and measurement conditions
The two results are Mifflin–St Jeor (1990) and revised Harris–Benedict (1984) predictions. They are not separate measurements under resting and basal protocols.
At male coefficients, 70 kg, 175 cm and age 30, Mifflin gives 1,648.75 kcal/day and revised Harris–Benedict gives 1,695.667 kcal/day. The difference is 46.917 kcal/day, about 2.85% of Mifflin; it is not a guaranteed 10–20% gap. It changes when inputs change.
Basal measurement uses controlled resting and post-absorptive conditions. Resting-energy prediction instead substitutes inputs into a regression equation. FAO/WHO/UNU definitions distinguish basal conditions and total expenditure. This form does not perform calorimetry.
Total daily expenditure includes energy beyond rest. A selected numerical product is not a measurement of that expenditure, a minimum food allowance, or a verified maintenance intake. There is no fixed percentage gap between the displayed equations.
Using the comparison
Equation output is predicted resting energy, not measured metabolism or a food-intake target. No automatic deficit, surplus, macronutrient prescription, weekly weight forecast, or medical metabolism grade is inferred.
A study population describes the evidence behind an equation. It does not establish suitability for every person with the same age or measurements, or for illness, pregnancy, lactation, or childhood. Individual nutrition decisions require information beyond these inputs.
Compare the named coefficients and reproduce the worked example. The existing Harris–Benedict comparison remains available when this Mifflin form accepts the inputs, without implying that the same age policy applies to the standalone Harris–Benedict tool.
Frequently Asked Questions
Does this measure my metabolism?
No. The output comes from a named equation, using the values entered. Indirect calorimetry is a different measurement process.
Which equation is best for me?
This tool does not rank equations for an individual. Different coefficients and research populations can produce different predictions without proving which prediction is closest to a measurement.
Should I eat the displayed number of calories?
The results are educational equation values and, where available, selected multiplier scenarios. They do not prescribe food intake or forecast weight change.
Why does changing an input remove the result?
A displayed result belongs to the inputs submitted. Editing a contributing field clears it so an old result is not mistaken for a new calculation.
Sources and interpretation
Publication: Mifflin et al., February 1990, DOI 10.1093/ajcn/51.2.241. Original paper facsimile. Sources checked on 2026-09-30; this access date is separate from publication.
Publication: Roza and Shizgal, July 1984, DOI 10.1093/ajcn/40.1.168. The retained coefficients come from Table 3, equations 3 and 6, based on 337 historical subjects including older adults. The paper reports limits for malnourished patients; its study statistics are not individual guarantees.
Historical context: Harris and Benedict (December 1918), original paper, page 373. The adult series had 136 men and 103 women. The tabulated ages 21–70 are not universal validation bounds. Sources checked on 2026-09-30.
NIST Handbook 44 (2026), Appendix C: 1 lb = 0.45359237 kg; 1 in = 2.54 cm.