Estimated maintenance calories and activity levels
Resting energy is multiplied by the selected activity factor to estimate maintenance needs. Other figures are arithmetic offsets for comparison; individual response varies. The activity multiplier is shown separately. All energy outputs and the preset table follow your chosen energy unit; the scenario offsets still represent 250, 500 and 300 kcal/day.
To compare weight with height separately, the BMI Calculator reports the adult screening range, which does not measure energy needs.
The formula
W is kilograms, H is centimetres, A is age, and S is +5 for the male constant or −161 for the female constant. Daily expenditure equals RMR times activity factor. Kilojoule display multiplies every energy result by 4.184. Custom activity mode replaces the preset multiplier; changing activity modes retains the previous entry.
A moderately active 30-year-old
For 70 kg, 175 cm, age 30 using the male constant, RMR is 1,648.75 kcal/day. A 1.55 activity factor gives about 2,555.6 kcal/day.
How to use this calculator
- Choose metric or US customary units and enter age, height and weight. Unit switches convert the same measurements.
- Choose a preset activity level or enter a custom factor, then select kcal/day or kJ/day.
- Read the live resting and maintenance estimates; expand the table to compare the five preset activity levels.
Activity is the largest estimate
The equation estimates energy at rest from population averages. The activity category introduces more uncertainty.
Choose a typical week rather than the most active day.
Use trends rather than one exact number
Food labels, portions, metabolism, and activity estimates all contain error.
Medical conditions, pregnancy, medications, growth, and training can require individualized guidance.
Compare activity assumptions and energy units
The table recalculates maintenance for all five preset multipliers using your same resting estimate. It shows how much the activity assumption changes the total without requiring repeated edits. Custom mode accepts a multiplier from 1 to 3 and shows it alongside your chosen result; it does not change the preset comparison rows.
One dietary kilocalorie converts to 4.184 kJ under the thermochemical convention used here. For the default example, 1,978.5 kcal/day becomes 8,278.044 kJ/day before display rounding. The below-maintenance and above-maintenance comparisons are converted after their kcal offsets are applied. A unit change therefore leaves the physical energy estimate unchanged.
Assumptions & limitations
What this calculation assumes
- Adult age 19–100 and stable measurements; ages above the original study population are extrapolations.
- Mifflin–St Jeor constants and a preset or user-entered activity multiplier.
- Deficit and surplus values are arithmetic comparisons.
What to keep in mind
- This estimate is not a meal plan, diagnosis, or prescription.
- The equation excludes pregnancy, illness, and adaptive changes.
- Very low targets can be inappropriate.
- The original Mifflin–St Jeor study included adults aged 19–78, so older-age estimates carry additional uncertainty.
Common questions
What is BMR versus maintenance?
Resting energy covers rest; maintenance multiplies it by activity.
Why are deficits not a weight-loss promise?
Expenditure and weight response vary over time.
Which activity level should I choose?
Use a typical long-term pattern, considering exercise and physical work.
Does switching to kilojoules change the estimate?
It converts the same energy by 4.184 kJ per kcal. The comparison offsets remain defined in kcal and are converted with the result.
Sources & further reading
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