Weight Loss Calculator (Deficit + Timeline)
Daily calorie target and target date from current and goal weight, Mifflin-St Jeor BMR, and activity multiplier.
HEALTHCalculate the daily calorie target needed to reach your goal weight by a target date. Uses Mifflin-St Jeor BMR plus an activity multiplier to find your maintenance (TDEE), then applies your chosen calorie deficit (250, 500, 1,000, or custom) and projects weekly loss and finish date.
A 3,500-calorie cumulative deficit ≈ 1 lb of fat loss. So a 500 cal/day deficit produces ~1 lb/week. Mifflin-St Jeor BMR: Male = 10×weight(kg) + 6.25×height(cm) - 5×age + 5. Female: -161 instead of +5. TDEE = BMR × activity factor (1.2 sedentary up to 1.9 very active). Aim for 0.5-1% of body weight loss per week to preserve muscle and avoid the metabolic slowdown that comes with aggressive deficits. Recalculate every 10-15 lbs lost.
Weight Loss Calculator (Calorie Deficit + Timeline)
Calculate how many calories per day you need to eat to reach a target weight by a target date. Uses Mifflin-St Jeor BMR plus an activity multiplier to find your maintenance, then sets the deficit needed to hit your goal.
Notes
- Pace under 1% of body weight per week preserves muscle and is easier to sustain.
- Larger deficits (1,000+ cal) work short-term but increase lean mass loss and trigger metabolic adaptation.
- Recalculate every 10-15 lbs lost - your TDEE drops as you lose weight.
How Weight Loss Math Works
The simple rule of thumb: a 3,500-calorie cumulative deficit equals one pound of fat loss. A 500 calorie/day deficit produces about 1 lb/week (3,500 cal/week ÷ 7 days). This is approximate - the actual ratio depends on body composition, water shifts, and metabolic adaptation, but it is a reasonable target for planning.
BMR = your body's baseline energy needs at complete rest. The Mifflin-St Jeor equation: Male: 10×weight(kg) + 6.25×height(cm) − 5×age + 5. Female: −161 instead of +5. TDEE = BMR × activity multiplier (1.2 sedentary up to 1.9 very active). Eat at TDEE to maintain; eat below TDEE for the deficit needed for your target loss rate.
Aim for 0.5-1% of body weight per week. A 200 lb person can lose 1-2 lb/week sustainably with a 500-1,000 cal/day deficit. Going faster than 1% per week increases muscle loss, slows your metabolism (adaptive thermogenesis), and is rarely sustainable. Plateaus around weeks 6-12 are normal - either tighten the deficit, take a 1-2 week diet break at maintenance, or accept slower progress.
Estimates only. Individual results vary substantially with body composition, sleep, hormones, medications, and metabolic adaptation. Consult a doctor or registered dietitian before starting a significant diet, especially if you have a medical condition.