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Calculate calorie deficit needed to lose weight: enter current weight, goal weight, weeks and TDEE to see daily deficit and intake.
Calculate calorie deficit needed to lose weight: enter current weight, goal weight, weeks and TDEE to see daily deficit and intake.
Enter values above and click Calculate — results will appear here with the formula explained.
A sustainable calorie deficit is planned as maintenance calories minus a daily energy gap chosen to trade pace against side effects: roughly 500 kcal per day yields about half a kilo per week before adaptation, while 300 kcal is slower but preserves muscle and adherence. The calculator derives maintenance from Mifflin-St Jeor plus activity, then subtracts your chosen deficit, flagging any target that falls below basal metabolic rate where nutrient adequacy becomes precarious. Weekly deficit multiplied by seven divided by roughly 7,700 kcal per kilogram of tissue converts the daily gap into expected weekly loss, linking the arithmetic to scale expectations.
Deficit sizing is physiological and behavioral, not just mathematical. Aggressive cuts sacrifice lean mass, sleep and training quality, while moderate cuts survive weekends and stress; periodic re-estimation as body mass falls keeps the plan honest rather than chasing a single initial number into diminishing returns.
The 7,700 kcal/kg rule is an approximation with known error bands: early rapid drops are mostly glycogen-water (each gram glycogen binds ~3 g water), fat loss runs closer to 7,700 while lean-inclusive loss runs lower, and metabolic adaptation trims 5–15% off predicted expenditure over months. Judge by 2–4 week scale trends, never daily noise.
Floor safety matters more than speed: intakes below ~1,200 (women) / 1,500 (men) risk micronutrient gaps, hormonal disruption, gallstones and binge-rebound cycles. Very-low-calorie protocols belong under medical supervision with labs and refeeding plans — this calculator flags sub-floor targets rather than endorsing them.
Protein and resistance training decide what the deficit burns: 1.6–2.2 g/kg protein plus 2–4 weekly sessions preserve lean mass, keeping 75–85% of loss as fat versus 60% on diet-only crash plans. Sleep 7–9 hours — short sleep raises ghrelin, lowers leptin and measurably slows fat loss at identical deficits.
Plateaus are physiological, not failure: water retention masks fat loss for weeks (especially with new training, sodium shifts and cycles), then 'whooshes' release. Break genuine stalls (4+ weeks flat at verified intake) by recalculating TDEE at the new lower weight, adding 2,000 daily steps, or implementing 1–2 week diet breaks at maintenance before resuming.
Calculate calorie deficit needed to lose weight: enter current weight, goal weight, weeks and TDEE to see daily deficit and intake. Formula: Total deficit = (current-goal)*7700 kcal.
A sustainable calorie deficit is planned as maintenance calories minus a daily energy gap chosen to trade pace against side effects: roughly 500 kcal per day yields about half a kilo per week before adaptation, while 300 kcal is slower but preserves muscle and adherence. The calculator derives maintenance from Mifflin-St Jeor plus activity, then subtracts your chosen deficit, flagging any target that falls below basal metabolic rate where nutrient adequacy becomes precarious. Weekly deficit multiplied by seven divided by roughly 7,700 kcal per kilogram of tissue converts the daily gap into expected weekly loss, linking the arithmetic to scale expectations.
Deficit sizing is physiological and behavioral, not just mathematical. Aggressive cuts sacrifice lean mass, sleep and training quality, while moderate cuts survive weekends and stress; periodic re-estimation as body mass falls keeps the plan honest rather than chasing a single initial number into diminishing returns.
The 7,700 kcal/kg rule is an approximation with known error bands: early rapid drops are mostly glycogen-water (each gram glycogen binds ~3 g water), fat loss runs closer to 7,700 while lean-inclusive loss runs lower, and metabolic adaptation trims 5–15% off predicted expenditure over months. Judge by 2–4 week scale trends, never daily noise.
Floor safety matters more than speed: intakes below ~1,200 (women) / 1,500 (men) risk micronutrient gaps, hormonal disruption, gallstones and binge-rebound cycles. Very-low-calorie protocols belong under medical supervision with labs and refeeding plans — this calculator flags sub-floor targets rather than endorsing them.
Protein and resistance training decide what the deficit burns: 1.6–2.2 g/kg protein plus 2–4 weekly sessions preserve lean mass, keeping 75–85% of loss as fat versus 60% on diet-only crash plans. Sleep 7–9 hours — short sleep raises ghrelin, lowers leptin and measurably slows fat loss at identical deficits.
Plateaus are physiological, not failure: water retention masks fat loss for weeks (especially with new training, sodium shifts and cycles), then 'whooshes' release. Break genuine stalls (4+ weeks flat at verified intake) by recalculating TDEE at the new lower weight, adding 2,000 daily steps, or implementing 1–2 week diet breaks at maintenance before resuming.
From 80kg to 75kg in 10 weeks: 5kg × 7700 = 38,500 total, daily deficit ~550, with TDEE 2500 target ~1,950/day. Expect weeks 1–2 to drop faster (water), then settle near 0.5 kg/week of true tissue.
Formulas are standard public references (see our methodology). External standards are cited in the text where they apply.
Last reviewed: September 2026 · Report an error