Calorie Calculator

BMR vs. TDEE, and where the numbers come from

This uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) — roughly what your body burns at rest — then multiplies it by an activity factor to get Total Daily Energy Expenditure (TDEE), your rough maintenance calories. Mifflin-St Jeor is generally considered more accurate for most people than the older Harris-Benedict equation, which is why it's the one used here.

From there it shows estimates for mild weight loss, faster weight loss, and weight gain, based on the standard ~7,700 kcal-per-kilogram (about 3,500 kcal-per-pound) rule of thumb for how much stored energy a given amount of body weight represents. These are estimates for general planning, not medical advice — actual needs vary by individual, and factors like sleep, stress, medical conditions, and non-exercise daily movement can shift real-world numbers meaningfully from the formula's prediction.

Picking an honest activity level

The activity multiplier is the part people most often overestimate — "moderate" is meant for genuine structured exercise 3-5 days a week, not just a generally busy schedule. Overestimating activity level is the single most common reason someone's real-world weight trend doesn't match what a calorie calculator predicted; if results seem off after a few consistent weeks of actually tracking intake, trying one activity level lower is a reasonable first adjustment.

TDEE shifts as your weight changes

Maintenance calories aren't fixed — TDEE drops as body weight drops, because a smaller body burns fewer calories at rest and during the same activity. This is the real mechanical reason weight loss commonly stalls partway through a diet even with no change in habits: the deficit that worked at a higher starting weight shrinks as weight comes down, since maintenance calories are chasing the new, lower weight downward too. Recalculating every 10-15 pounds of change (rather than once at the start) keeps the estimate honest through the whole process.

What a realistic rate of loss looks like

A 500 kcal/day deficit works out to roughly one pound (about 0.45kg) lost per week, based on the ~3,500 kcal-per-pound rule this calculator's estimates use — faster loss requires a larger deficit, which becomes harder to sustain and more likely to cost lean muscle rather than only fat. Widely cited general guidance favors roughly 0.5-1% of body weight lost per week as a sustainable range for most people, which is worth checking the "weight loss" and "mild weight loss" figures above against for your own starting weight, rather than assuming faster is automatically better.