Calorie Calculator

Estimate daily calories with the Mifflin-St Jeor formula.

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Reviewed by Calcora OnlineLast updated May 13, 2026.
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Calorie Calculator Guide

Read the step-by-step guide for inputs, formula notes, common mistakes, and result interpretation.

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What does a calorie calculator estimate?

A calorie calculator estimates daily energy needs from body measurements, age, sex, and activity level. It is often used as a starting point for weight maintenance, fat loss, or muscle gain planning.

The result is an estimate, not a personal nutrition prescription. Real energy needs can differ because of body composition, activity patterns, health conditions, and tracking accuracy.

Calorie calculation method

Many calorie calculators estimate BMR first and then multiply it by an activity factor to estimate daily maintenance calories.

Daily Calories = BMR x Activity Factor

Example daily calorie estimate

If estimated BMR is 1,650 calories and the activity factor is 1.55, estimated daily maintenance is about 2,558 calories.

A fat loss target may use a moderate deficit below maintenance, while a muscle gain target may use a controlled surplus.

How to interpret calorie needs

The result is best treated as a starting target. Body weight trends over several weeks can show whether the estimate is too high, too low, or close enough.

If weight is stable, intake is likely near maintenance. If weight changes, actual energy balance is different from the estimate.

When to use this calculator

Use this calculator for meal planning, macro planning, weight goals, and understanding daily energy needs.

For medical nutrition, pregnancy, eating disorders, or chronic disease, professional guidance is more appropriate.

Calorie estimate limitations

Do not overestimate activity level. This is one of the most common reasons calorie targets are too high.

Do not cut calories aggressively without considering health, adherence, and performance.

What changes the Calorie Calculator result most?

Calorie Calculator changes most when weight, height, age, sex, activity level, and goal adjustment. Change one input at a time when comparing scenarios so you can see which assumption is responsible for the difference.

Activity level is often the most subjective input, so testing conservative and moderate activity assumptions can be helpful.

When the Calorie Calculator result can be misleading

The result can be misleading if activity level is guessed incorrectly, food intake is tracked inaccurately, or medical factors affect energy needs.

Wearable calorie estimates and food labels can both contain error, so the calculator should be adjusted using real progress.

Practical notes for the Calorie Calculator

Use weekly average body weight rather than one daily weigh-in when checking progress.

A sustainable calorie target is usually better than an extreme one that cannot be followed.

Use the result as a planning aid for weight maintenance, fat loss planning, muscle gain planning, macro targets, and meal planning. The calculator gives a calorie estimate, but the final target should also reflect real progress, activity consistency, food tracking accuracy, and personal health context.

How to reuse the Calorie Calculator result

Save the main inputs beside the answer. This makes the result easier to compare later and prevents confusion about which values produced the number.

Record the activity factor and goal setting with the calorie number so you know why the target was chosen.

How to read calorie needs

A calorie estimate is most useful when it is treated as a starting target, not a fixed rule. If the result is used for maintenance, compare it with body weight trends over two to four weeks. If weight is rising, the real maintenance number may be lower than the estimate; if weight is falling, the real maintenance number may be higher. Activity multipliers can also be easy to overestimate, so office workers, students, and remote workers often get a better first target by choosing a moderate or light setting unless their training schedule is consistent.

Frequently asked questions

Is the calorie result exact?

No. It is an estimate that should be adjusted using real progress.

Which activity level should I choose?

Choose the level that matches your normal routine, not your ideal routine.

Can I use this for weight loss?

Yes, as a starting point for a moderate calorie deficit.

Is this medical advice?

No. It is a general planning calculator.