Calorie Deficit Calculator
Turn a target weekly weight-loss rate into the daily calorie deficit and intake you need, with a built-in safety check.
A safe calorie deficit is roughly 500–1,000 kcal per day, which produces a gradual loss of 0.5–1 kg (1–2 lb) per week under CDC, WHO and AHA guidance.
How a calorie deficit works
A deficit simply means eating fewer calories than you burn; your body covers the gap from stored energy, mostly body fat, and you lose weight. Because a kilogram of body mass stores roughly 7,700 calories (about 3,500 per pound), your chosen weekly rate translates into a specific daily deficit. The tool subtracts that deficit from your maintenance calories to give a target intake.
You need your maintenance figure first — the TDEE calculator estimates it, and the BMR calculator shows the resting floor you shouldn't drop below for long. For a projected finish date, feed the same numbers into the weight-loss timeline calculator.
Choosing a safe deficit
Steady beats fast. Health authorities point to 0.5–1 kg (1–2 lb) per week — roughly a 500–1,000 kcal daily deficit — as the sustainable range that best preserves muscle. Bigger deficits work faster but are harder to hold and cost more lean tissue. The calculator flags rates above that, and target intakes that fall below sensible minimums. Once you have your intake, split it into protein, carbs and fat with the macro calculator.
Weekly rate and the deficit it needs
| Weekly rate | Daily deficit (kg / lb basis) | Note |
|---|---|---|
| 0.25 kg (~0.5 lb) | ~275 / 250 kcal | Conservative; good for lean people |
| 0.5 kg (~1 lb) | ~550 / 500 kcal | Typical target; within the safe range |
| 0.75 kg (~1.5 lb) | ~825 / 750 kcal | Moderate |
| 1 kg (~2 lb) | ~1,100 / 1,000 kcal | Top of the safe range |
| Over 1 kg (2 lb) | Over 1,100 / 1,000 kcal | Faster than guidelines; supervise |
Deficit = weekly rate × energy per unit ÷ 7 (7,700 kcal/kg; 3,500 kcal/lb). The kg and lb rows differ slightly because 1 kg = 2.2 lb.
Rates follow CDC/WHO/AHA guidance; intake minimums from the 2013 AHA/ACC/TOS guideline. The linear model overstates long-term loss (metabolism adapts) — estimate only, not medical advice.
Frequently asked questions
How is the daily calorie deficit calculated?
The calculator multiplies your target weekly weight-loss rate by the energy stored per unit of body mass (about 7,700 kcal per kg, or 3,500 kcal per pound) and divides by 7 days. For example, 0.5 kg/week × 7,700 ÷ 7 = 550 kcal/day. Your target daily intake is then your maintenance calories (TDEE) minus that deficit.
How big a calorie deficit is safe?
Most health authorities (CDC, WHO, AHA) consider a gradual loss of 0.5–1 kg (1–2 lb) per week the safest, most sustainable range, which is roughly a 500–1,000 kcal/day deficit. The 2013 AHA/ACC/TOS clinical guideline uses 500 or 750 kcal/day deficits as standard. Larger deficits raise the risk of muscle loss, nutrient gaps and rebound.
Why does the calculator warn me about a low target intake?
Very low intakes can under-supply protein, vitamins and minerals and accelerate lean-mass loss. As a guardrail the tool flags target intakes below about 1,200 kcal/day (women) or 1,500 kcal/day (men), thresholds from the 2013 AHA/ACC/TOS guideline. If a flag appears, choose a slower rate or consult a professional.
Why is my real weight loss slower than the number shown?
The 7,700 kcal/kg (3,500 kcal/lb) rule is a useful first approximation but assumes a fixed deficit. In practice, as you lose weight your resting energy expenditure declines, water and glycogen shift day to day, and adherence varies — so the rule tends to overestimate cumulative loss over months. Treat the estimate as a starting target and adjust from 2–4 weeks of real data.
Do I still need to exercise if I hit my deficit through diet?
You can create the deficit through diet alone, but the ACSM notes that around 150–250+ minutes of activity per week helps preserve lean mass, improves health markers, and supports keeping weight off. Exercise also lets you eat a little more while staying in a deficit. This is general information, not personalized advice.
Sources
- Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542-6 — Origin of 3,500 kcal/lb rule
- 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults (J Am Coll Cardiol. 2014) — 500/750 kcal deficits; 1,200/1,500 kcal minimums
- ACSM Position Stand: Physical Activity for Weight Loss and Prevention of Weight Regain (Med Sci Sports Exerc. 2009) — 150-250+ min/week activity for weight
- NIDDK (NIH) — Choosing a Safe & Successful Weight-Loss Program — Safe gradual weight-loss goal (NIH)
The thresholds and formulas used by this calculator follow the primary sources above. This tool provides general information, not personalised medical advice.