Weight Loss Calculator — Calories & Time to Lose Weight
Enter your stats and goal weight to see your TDEE, daily calorie target, expected weekly weight loss, and a week-by-week projection to your target.
kg
kg
cm
years
Biological sex
Activity level
kcal/day
Eat this amount each day to lose weight at the chosen rate
- 1
BMR (Mifflin–St Jeor)
10 × 90 + 6.25 × 175 − 5 × 30 + 5 = 1,849Male formula: 10W + 6.25H − 5A + 5 - 2
TDEE (BMR × activity factor)
1,849 × 1.55 = 2,866 - 3
Daily calorie target
2,866 − 500 = 2,366
How does this calculator work?
Daily calorie target = TDEE − deficit. TDEE comes from BMR (Mifflin–St Jeor) × activity factor. A 500 kcal/day deficit burns roughly 0.45 kg per week; 1,000 kcal/day burns about 0.9 kg/week. Time to goal ≈ (kg to lose × 7,700) ÷ daily deficit ÷ 7 weeks. Safe calorie floors: 1,500 kcal (men) and 1,200 kcal (women).
Formula
How this is calculated
The calculator estimates your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation — currently the most validated equation for adults: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, minus 161 for women. This is then multiplied by an activity factor (1.2–1.9) to give your Total Daily Energy Expenditure (TDEE) — the calories you burn maintaining your current weight. Eating below TDEE creates the deficit needed for fat loss.
The standard approximation used in clinical weight-management guidelines is that 7,700 kcal of cumulative deficit produces roughly 1 kg of fat loss. A daily deficit of 500 kcal gives about 0.45 kg per week; 1,000 kcal/day gives about 0.9 kg per week, which is near the 1 kg/week limit most dietitians recommend to preserve lean mass. The calculator enforces a safe minimum intake floor (1,500 kcal/day for men, 1,200 kcal/day for women) — if your chosen deficit would breach this, the effective deficit is capped at that floor.
The projection assumes your body weight, TDEE and deficit all stay constant throughout the timeline — in reality, TDEE decreases as you lose weight (a phenomenon called adaptive thermogenesis), so actual progress may slow. Recalculate every 4–6 weeks. The BMI at target is shown for reference using the standard BMI = weight(kg) / height(m)². This tool is a planning aid, not medical advice; consult a healthcare provider before starting any weight-management programme.
Frequently asked questions
Approximately 1,100 kcal/day below your TDEE (1 kg × 7,700 kcal ÷ 7 days). In practice most dietitians cap the recommendation at a 500–1,000 kcal deficit to prevent muscle loss and nutrient deficiencies.
Two main reasons: (1) your TDEE falls as you weigh less — a smaller body burns fewer calories. (2) Adaptive thermogenesis — the body partially compensates for the deficit by reducing metabolic rate. Both effects shrink the effective deficit over time, so you need to periodically recalculate or reduce intake further.
Most clinical guidelines recommend at least 1,200 kcal/day for women and 1,500 kcal/day for men to ensure sufficient nutrient intake and avoid excessive lean-mass loss. Very low calorie diets (below 800 kcal) should only be undertaken under medical supervision.
Also known as
TG we-Calculate Editorial Team. (2026). Weight Loss Calculator — Calories & Time to Lose Weight [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/weight-loss-calculator
TG we-Calculate Editorial Team. "Weight Loss Calculator — Calories & Time to Lose Weight." TG we-Calculate. 2026. https://we-calculate.com/calculator/weight-loss-calculator.
TG we-Calculate Editorial Team, "Weight Loss Calculator — Calories & Time to Lose Weight," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/weight-loss-calculator
@misc{wecalculate_weight_loss_calculator, title = {Weight Loss Calculator — Calories & Time to Lose Weight}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/weight-loss-calculator}}, year = {2026}, note = {TG we-Calculate} }
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