Calculation details
Energy-needs estimate only, not medical nutrition advice. Population equations and activity factors can differ from measured individual needs; discuss health decisions with a qualified clinician.
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Use this result
Share the current inputs or ask ChatGPT to explain the calculation in context.
What does this calculator estimate?
A calorie calculator estimates daily maintenance calories. Enter age, sex, height, weight, and activity level to see the target.
- Mifflin-St Jeor BMR × activity factor
- Maintenance ≈ 2,140 kcal in the example
- Subtract 300–500 for weight loss
How calorie needs are estimated
Daily calorie needs start with the basal metabolic rate — the energy your body uses at rest — estimated by the Mifflin-St Jeor equation, then multiplied by an activity factor. The result is the maintenance level: eat that to stay, less to lose, more to gain.
Limitations to watch for
The estimate is a starting point, not a measurement — real needs vary by muscle mass, genetics, and daily activity. A 300–500 kcal deficit is a sustainable weight-loss range. Recalculate as weight changes.
How to use it in practice
Enter your details and activity honestly (most people overestimate). Use the maintenance number as the baseline, then set a modest deficit or surplus. Track weight for two weeks and adjust by 100–200 kcal.
['Enter age, sex, height, and weight.', 'Choose the activity level honestly.', 'Read the maintenance calories.']
How this calculator works
Formula
Estimates daily calories with the Mifflin-St Jeor equation: BMR = 10×kg + 6.25×cm − 5×age + 5 (male) or −161 (female), then multiplied by an activity factor (1.2–1.9).
Worked example
A 30-year-old male, 180 lb, 5'10", sedentary: BMR ≈ 1,783 → maintenance ≈ 2,140 calories/day.
Assumptions to verify
- The Mifflin-St Jeor equation applies.
- The activity factor is realistic.
- Weight-change goals use standard deficit/surplus ranges.
Frequently asked questions
How do I calculate daily calories?
Mifflin-St Jeor BMR × activity factor: BMR 1,783 × 1.2 ≈ 2,140 kcal in the example.
What is BMR?
Basal metabolic rate — the calories your body burns at rest just to function.
How much should I cut to lose weight?
A 300–500 kcal daily deficit loses about 0.5–1 lb per week.
What activity factor should I use?
Be honest: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active.
Is this exact?
No — it's an estimate. Track your weight and adjust by 100–200 kcal.
Why do I need more calories than my friend?
Size, muscle mass, age, and activity all change the number.
Should I eat back exercise calories?
Generally not — exercise calories are overestimated by trackers.
Cite this tool
BoringToolsKit. “Calorie Calculator.” boringtoolskit.com/calorie-calc/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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