How are daily calories calculated?

BMR from the Mifflin-St Jeor equation is multiplied by an activity factor for maintenance, then a goal adjustment of ±500 kcal is applied.

What deficit should I use to lose weight?

Around 500 kcal a day targets roughly 0.45 kg per week. Larger deficits are harder to sustain and can backfire.

Why is maintenance higher than BMR?

BMR is resting energy. Maintenance adds the calories you burn through daily activity and exercise via the activity factor.

How accurate is the estimate?

It's a solid starting point, but metabolism varies. Track results over a few weeks and adjust the target as needed.

Should I eat back exercise calories?

The activity factor already includes typical exercise, so adding more on top risks double-counting. Adjust by results instead.

Can I share a calculation?

Yes. Use Share to copy a link that reopens the calculator with the same details.

Calorie calculator

Enter your weight, height, age, and sex, pick an activity level and a goal, and the calculator estimates the calories you need each day, along with your maintenance level and BMR.

Use it to find a daily calorie target for maintaining, losing, or gaining weight.

Daily calories

2,759 kcal

Maintenance: 2,759 kcal
BMR: 1,780 kcal

The result updates as you type. The headline is your goal calories; maintenance is what holds your weight, and BMR is your resting baseline. This calorie target is an estimate only. It does not replace medical or dietetic advice — talk to a healthcare professional before changing your diet.

How does it work?

Maintenance is BMR times the activity factor. A 500 kcal daily deficit or surplus targets roughly 0.45 kg of change per week. Adjust to real results over a few weeks.

Daily calorie formula

\text{cal} = \text{BMR} \times \text{activity} + \text{goal}

cal: Daily calorie target.
BMR: Basal metabolic rate (Mifflin-St Jeor).
activity: Activity factor, 1.2 to 1.9.
goal: Adjustment: 0 maintain, −500 lose, +500 gain.

An 80 kg, 180 cm, 30-year-old man (BMR 1780) who is moderately active maintains on about 2759 kcal; to lose weight, around 2259.

Expert tips

This calorie target is an estimate only. It does not replace medical or dietetic advice — talk to a healthcare professional before changing your diet.

Method & sources

BMR uses the Mifflin-St Jeor equation. Activity factors run from 1.2 (sedentary) to 1.9 (athlete). Losing or gaining adjusts the target by 500 kcal a day (about 0.45 kg/week).

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

A new predictive equation for resting energy expenditure in healthy individuals — Mifflin et al., American Journal of Clinical Nutrition (1990), verified 2026-06-10

How we calculate

BMR uses the Mifflin-St Jeor equation.
Activity factors run from 1.2 (sedentary) to 1.9 (athlete).
Losing or gaining adjusts the target by 500 kcal a day (about 0.45 kg/week).
This is general guidance, not medical or dietetic advice.

Limitations

This calorie target is an estimate only. It does not replace medical or dietetic advice — talk to a healthcare professional before changing your diet.

Rounding

Calories are shown as whole numbers. The calculation uses full precision.

What this calculator does

Your daily calorie need is your resting metabolism scaled up for activity. This calculator estimates BMR with the Mifflin-St Jeor equation, multiplies by an activity factor for maintenance, then adjusts for your goal.

How to use it

Enter your weight, height, age, and sex.
Pick the activity level that matches your week.
Choose a goal: maintain, lose, or gain.
Read the daily calorie target.

A worked example

An 80 kg, 180 cm, 30-year-old man (BMR 1780) who is moderately active maintains on about 2759 kcal. To lose weight, the target drops to around 2259.

Choosing an activity level

Sedentary is mostly sitting; lightly active adds light exercise a few days; moderately active is exercise most days; very active and athlete are for hard training or physical jobs. When unsure, pick the lower one and adjust by results.

Common mistakes

Overestimating activity, which inflates the target.
Expecting fast results from a large deficit.
Ignoring real-world change — adjust after a few weeks.

When it's useful

Setting a calorie goal for a diet, planning for weight change, or checking whether your current intake matches your activity.

FAQ

How are daily calories calculated?: BMR from the Mifflin-St Jeor equation is multiplied by an activity factor for maintenance, then a goal adjustment of ±500 kcal is applied.
What deficit should I use to lose weight?: Around 500 kcal a day targets roughly 0.45 kg per week. Larger deficits are harder to sustain and can backfire.
Why is maintenance higher than BMR?: BMR is resting energy. Maintenance adds the calories you burn through daily activity and exercise via the activity factor.
How accurate is the estimate?: It's a solid starting point, but metabolism varies. Track results over a few weeks and adjust the target as needed.
Should I eat back exercise calories?: The activity factor already includes typical exercise, so adding more on top risks double-counting. Adjust by results instead.
Can I share a calculation?: Yes. Use Share to copy a link that reopens the calculator with the same details.

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