Calorie Deficit Calculator — Lose Weight
Calculate your safe daily calorie deficit to lose weight. Get TDEE, target intake and projected weekly loss estimate. Based on Mifflin-St Jeor. Free.
Your Calorie Deficit Plan
Fill in the form and press Calculate Deficit to see your personalised plan.
CalcVita. (2026). Calorie Deficit Calculator — Lose Weight. CalcVita. Retrieved June 4, 2026, from https://calcvita.com/en/calculators/calorie-deficit
How It Works
Enter your sex, age, weight, height, and activity level. The calculator computes your BMR using the Mifflin-St Jeor equation, then multiplies by an activity factor to get your TDEE (Total Daily Energy Expenditure — the calories you burn each day). Choose a deficit tier (250–1000 kcal/day below TDEE) to get your target daily intake and projected weight loss rate.
The Formula
BMR (Mifflin-St Jeor, 1990): Men: 10×weight + 6.25×height − 5×age + 5. Women: 10×weight + 6.25×height − 5×age − 161. TDEE = BMR × activity multiplier (1.2 sedentary → 1.9 very active). Weight loss projection: 1 kg of fat ≈ 7,700 kcal deficit.
Deficit Tiers
−250 kcal/day (gentle): ~0.23 kg/week. Low risk, easier to sustain. −500 kcal/day (moderate): ~0.45 kg/week. Standard guideline. −750 kcal/day (significant): ~0.68 kg/week. Requires careful food choices. −1000 kcal/day (aggressive): ~0.91 kg/week. Only suitable for high-TDEE individuals.
Safe Minimum Intakes
This calculator enforces the minimum safe intakes: ≥1200 kcal/day for women and ≥1500 kcal/day for men. Going below these thresholds risks muscle wasting, micronutrient deficiencies, gallstones, and metabolic slowdown. Always consult a registered dietitian for personalised plans.
Practical Tips
Start with a −500 kcal/day deficit. It is sustainable for most people and produces about 0.5 kg/week without excessive hunger or fatigue.
Prioritise protein (1.6–2.2 g/kg body weight) during a deficit to protect muscle mass. Protein also increases satiety and has a high thermic effect.
Track adherence, not perfection. A consistent moderate deficit beats an aggressive deficit abandoned after 2 weeks.
Scientific Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7. PMID 2305711
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–37. PMID 21872751
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy non-obese and obese adults. J Am Diet Assoc. 2005;105(5):775–89. PMID 15466943
- Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370–3.
- What is a calorie deficit?
- A calorie deficit occurs when you consume fewer calories than your body burns. When your body has less energy available than it needs, it turns to stored fat for fuel, resulting in weight loss. A deficit of 500 kcal/day theoretically produces about 0.45 kg (1 lb) of fat loss per week.
- How many calories should I cut to lose weight?
- For safe, sustainable weight loss, most guidelines recommend a deficit of 500–750 kcal/day, targeting 0.5–0.7 kg (1–1.5 lb) per week. Deficits above 1000 kcal/day risk muscle loss, nutritional deficiencies, and metabolic adaptation. The minimum safe intake is 1200 kcal/day for women and 1500 kcal/day for men.
- Is a 1000 calorie deficit too much?
- A 1000 kcal/day deficit is aggressive and may be appropriate for individuals with high TDEE (e.g., 2800+ kcal/day), but it carries risks: muscle loss, fatigue, micronutrient gaps, and long-term metabolic slowdown. This calculator enforces safe minimum intakes and will cap your deficit if it would bring you below the floor.
- How accurate is this calorie deficit calculator?
- This calculator uses the Mifflin-St Jeor equation, validated as the most accurate non-calorimetric BMR formula for most adults (error ±10%). TDEE estimates include typical activity multipliers. Actual weight loss depends on body composition, adherence, hormonal factors, and metabolic adaptation — treat projections as planning guides, not guarantees.
- Why does the calculator show a smaller deficit than I requested?
- If your requested deficit would push your daily intake below the safe minimum (1200 kcal women / 1500 kcal men), the calculator automatically limits your deficit to keep intake at that floor. Very low intakes are associated with muscle loss, micronutrient deficiencies, and metabolic slowdown.
Suggested article
Calorie Deficit: The Science of Safe, Sustainable Weight Loss
A calorie deficit is the only proven mechanism for fat loss. Learn how large a deficit to create, how to protect muscle while losing fat, and why the math isn't always as simple as it looks.
Read the full article →More calculators
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