Calorie Calculator

About this calculator

A free daily calorie calculator that estimates how many calories your body uses in a day. It computes your resting metabolic rate (BMR) with the Mifflin-St Jeor equation, scales it by an activity multiplier to a Total Daily Energy Expenditure (TDEE), then adjusts that number for your goal — maintenance keeps you level, weight loss subtracts about 500 calories a day, and muscle gain adds about 300. Everything runs in your browser, no account or upload required. The result is a general screening estimate, not medical, nutritional, or dietary advice; individual needs vary with body composition, health, and medication, so consult a qualified professional before changing your diet.

From BMR to TDEE

The calculator starts with your basal metabolic rate (BMR) — the energy your body uses at complete rest to keep basic functions running. It estimates BMR with the Mifflin-St Jeor equation, a widely used screening formula that reads your sex, age, weight, and height. BMR is only the baseline; almost nobody spends a full day at rest.

To reach a daily figure the tool scales BMR by an activity multiplier, producing your Total Daily Energy Expenditure (TDEE) — the calories you burn across a typical day once movement, exercise, and the work of digestion are included. The higher the activity level you select, the larger the multiplier, and the larger your estimated TDEE.

What the activity multiplier means

The activity level is a single setting that stands in for everything you do beyond resting: a sedentary desk routine sits near the bottom, while regular hard training sits near the top. Because it is one rough factor rather than a tracked measurement, two people with the same BMR can have meaningfully different real-world expenditure, so pick the level that best matches a normal week and adjust if your results drift.

Small changes in this setting move the TDEE more than people expect, which is why the same body can show different daily targets depending on the activity choice. Treat it as the main dial for tailoring the estimate to your routine.

How the goal offsets translate to weekly change

Maintenance keeps your target at TDEE, so intake and expenditure roughly balance. The weight-loss goal subtracts about 500 calories a day, a moderate deficit that adds up to a change of roughly half a kilogram of body mass over a week. The muscle-gain goal adds about 300 calories a day, a leaner surplus meant to fuel new tissue while limiting excess fat.

These offsets are conservative defaults, not personalized prescriptions. Actual results vary with body composition, sleep, training, and how accurately intake is tracked, so use the number as a planning anchor and review your own trend over several weeks rather than expecting an exact match.

A screening estimate, not advice

Every figure here is a general screening estimate produced from a formula, not a measurement of your actual metabolism and not medical, nutritional, or dietary advice. Calorie needs shift with body composition, health conditions, pregnancy, and medication, and an equation cannot account for all of that.

Before changing what you eat or starting a deficit or surplus, consult a doctor or registered dietitian who can tailor a plan to your situation. The calculator is a starting point for that conversation, not a substitute for it.

By variant

• Maintain Weight
• Lose Weight
• Gain Muscle

Questions

How does the calorie calculator work?

It uses the Mifflin-St Jeor equation to estimate your basal metabolic rate from sex, age, weight, and height, multiplies that by a standard activity factor to get your TDEE, then applies a calorie offset for your goal. It is a widely used screening formula, not a measurement of your actual metabolism.

Is this medical or dietary advice?

No. The numbers are a general estimate for planning purposes only and are not medical, nutritional, or dietary advice. Calorie needs vary with body composition, health conditions, pregnancy, and medication, so consult a doctor or registered dietitian before changing what you eat.

Why do weight-loss and muscle-gain targets differ from maintenance?

Maintenance is your estimated TDEE. To lose weight the tool subtracts about 500 calories a day, a moderate deficit of roughly half a kilogram a week; to gain muscle it adds about 300 calories a day, a lean surplus meant to limit excess fat gain. These offsets are conservative defaults, not personalized prescriptions.

Is the calculator free and private?

Yes. It is free, needs no account, and runs entirely in your browser — none of the figures you enter are uploaded or stored.