How Many Calories Should I Eat a Day?
Published 2026-11-02
“How many calories should I eat?” is one of the most-searched health questions online. The useful answer is not a single number from a poster. It is your basal metabolic rate (BMR) scaled by an activity factor — a total daily energy expenditure (TDEE) estimate.
Use the free tool
Run these formulas with your own numbers. Math stays in your browser.
Open Calorie Calculator →This guide uses the same Mifflin-St Jeor math as our calorie calculator. It is a planning sketch, not medical advice. Age, muscle mass, medication and medical conditions can move the real figure by hundreds of calories.
Open the calorie calculator
Enter sex, age, height, weight and activity on the free calorie calculator. You will see maintenance calories plus slower and faster loss or gain targets. The BMR calculator shows the resting figure alone if you want that step first.
The formula search engines expect
Mifflin-St Jeor (1990) is the usual adult estimate in US clinical nutrition writing. It predicts resting calories from weight in kilograms, height in centimeters and age in years. Harris-Benedict is an older alternative; our BMR tool shows both.
BMR = 10 × kg + 6.25 × cm − 5 × years + 5
BMR = 10 × kg + 6.25 × cm − 5 × years − 161
TDEE ≈ BMR × activity factor
Activity factors
The factor is a multiplier, not extra food you “earn” after one workout. Pick the row that matches a typical week, not your best day.
| Lifestyle | Factor | Example |
|---|---|---|
| Sedentary | 1.2 | Desk work, little exercise |
| Light | 1.375 | Walks or 1–3 easy workouts |
| Moderate | 1.55 | 3–5 workouts a week |
| Very active | 1.725 | Hard training most days |
| Extra active | 1.9 | Physical job plus training |
Worked example
A 30-year-old man, 80 kg, 178 cm: BMR = 10×80 + 6.25×178 − 5×30 + 5 = 800 + 1,112.5 − 150 + 5 = 1,767.5 kcal. At a moderate 1.55 factor, TDEE is about 2,740 kcal. A 500 kcal daily deficit is about 2,240 kcal — a common slow-loss sketch, not a prescription.
A pound of body fat is often taught as ~3,500 kcal. That is a classroom average, not a promise that 500 kcal/day for 7 days equals one pound on the scale. Water, glycogen and the weekend can hide a week of work.
How to use the number
Maintenance is the calories that keep weight roughly stable. A 250–500 kcal daily gap is the usual planning band for gradual change. Larger gaps are harder to sustain and more likely to cut protein and training quality.
- Weigh and measure in the units the form asks for (or use the US fields; the tool converts).
- Pick the activity row that matches most weeks, not a race week.
- Read maintenance first, then the loss or gain lines.
- Hold the target for two to three weeks before you change it.
- Use the BMI and ideal-weight calculators only as context — they do not set calories.
What this estimate leaves out
Mifflin-St Jeor was validated on adults, not children, and it does not see muscle versus fat. Two people with the same height and weight can need different calories. Pregnancy, illness and some medications need a clinician, not this page. Food labels and restaurant calories are themselves estimates.
Search volume for “calorie calculator” and “how many calories should I eat” stays high on Google and Bing because the number changes when weight, age or training changes. Re-run the calorie calculator when any of those inputs move by more than a little, and use the BMR calculator if you only want the resting line. Protein, sleep and steps still matter more than a 50-calorie difference on a label.
Use the free tool
Run these formulas with your own numbers. Math stays in your browser.
Open Calorie Calculator →Frequently Asked Questions
Is 2,000 calories right for everyone?
No. That is a US Nutrition Facts reference, not your TDEE. Many adults sit above or below it.
Should I eat back exercise calories?
If you already chose an activity factor, you have already counted typical training. Adding a watch’s burn on top often double-counts.
Is BMR the same as TDEE?
BMR is rest. TDEE multiplies BMR by activity. Use the BMR calculator for the rest figure and the calorie calculator for the daily total.
Can I trust a watch more than this formula?
Wearables estimate burn with their own models and often miss. Treat both as ranges.
Is this medical advice?
No. Talk with a doctor or registered dietitian before a large calorie change.