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Weight Loss Calculator (Deficit + Timeline)

Daily calorie target and target date from current and goal weight, Mifflin-St Jeor BMR, and activity multiplier.

HEALTH

Calculate 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.

Disclaimer: Estimates only. Real results vary with body composition, sleep, hormones, medications, and metabolic adaptation. Consult a doctor or RD before significant dietary changes, especially with any medical condition.

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.

Current Weight (lbs)

Target Weight (lbs)

Height (inches)

Age

Sex at Birth

Activity Level

Weight Loss Pace

Target Daily Calories

2316 cal/day

Target Weight Loss-30.0 lbs

Basal Metabolic Rate (BMR)1817 cal

Maintenance (TDEE)2816 cal

Daily Deficit-500 cal

Weekly Weight Loss-1.00 lbs/wk

Weeks to Goal30.0 weeks

Estimated Target DateJanuary 28, 2027

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.

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Frequently Asked Questions

How many calories should I cut to lose 1 pound a week?

About 500 calories per day below your maintenance (TDEE). A 3,500-calorie cumulative deficit equals roughly 1 pound of fat loss, and 500 × 7 = 3,500. For 2 lb/week, aim for a 1,000 cal/day deficit, though this is aggressive and harder to sustain. Most adults do best at 300-500 cal below maintenance: slow enough to preserve muscle, fast enough to stay motivated.

Is it safe to lose 2 pounds a week?

For most healthy adults with excess weight, yes - 1 to 2 lb per week is the CDC and Academy of Nutrition and Dietetics recommended range. Faster than 2 lb/week (under medical supervision only) increases muscle loss, gallstone risk, and metabolic adaptation. Stay above 1,200 cal/day for women, 1,500 for men unless working with a doctor. Pair the deficit with 0.7-1.0 g protein per lb of goal body weight and resistance training to preserve muscle.

Why does my weight loss stall after a few weeks?

Two reasons. (1) Adaptive thermogenesis: your BMR drops as you lose mass and your body burns slightly fewer calories at rest. (2) Less non-exercise activity (NEAT): you unconsciously fidget less, walk slower, take more breaks. The calculator-recommended deficit shrinks effectively. Solutions: recalculate TDEE every 10-15 lbs lost; take a 1-2 week diet break at maintenance every 8-12 weeks; bump activity by 1 multiplier tier; or accept a slightly larger deficit.

How much weight can I realistically lose in 3 months?

At a sustainable 1-2 lb/week pace, 12-25 pounds over 3 months. The first 2-4 weeks often show faster loss (3-6 lbs/week) because of water weight and glycogen drop - this is not pure fat. After that, expect a steady 1-2 lb/week if you stay consistent. The calculator projects an idealized linear timeline; reality is bumpier with plateaus and small regains around stressful weeks or social events.

Do I really need to count calories?

Not necessarily, but it works. Apps like MyFitnessPal, Cronometer, MacroFactor make tracking easy for 2-4 weeks until you internalize portion sizes. After that, many people switch to portion-aware eyeballing or "every other day" tracking. Non-tracking approaches that work: protein-first plate composition (1 palm of protein + 2 fists of veggies + 1 cupped hand of carbs + 1 thumb of fat per meal), intermittent fasting (compresses eating window), and Mediterranean-style whole foods.

Weight Loss Calculator (Deficit + Timeline)

Weight Loss Calculator (Calorie Deficit + Timeline)

Notes

How Weight Loss Math Works

Frequently Asked Questions

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Weight Loss Calculator (Calorie Deficit + Timeline)

Notes

How Weight Loss Math Works