Free tools
Calorie deficit calculator.
Set a weekly rate and get a daily energy target, with an honest timeline to your goal weight.
How it works
A rate you can train on.
Pick how fast to go as a share of your bodyweight. Losing 0.5 to 1% a week is the range recommended for keeping muscle while dieting. The calculator turns that rate into a daily deficit, using the classic figure of about 7,700 kcal (32,200 kJ) per kilogram.
Change a week (kg) = weight × rate
Deficit a day = change a week × 7,700 kcal ÷ 7
Daily target = maintenance − deficit
Example: 90 kg at 0.5% is 0.45 kg a week, a deficit of 495 kcal (2,071 kJ) a day. From 11,000 kJ maintenance that's 8,929 kJ a day, and 90 to 80 kg takes at least 23 weeks.Why "at least". The 7,700 kcal figure only holds early on. As you lose weight your body uses less energy, so the same intake brings slower loss. Research by Hall and colleagues shows a fixed-number timeline over-promises, so treat the weeks as a floor and re-check your maintenance every few weeks.
Limits
- Your maintenance number is itself an estimate. Your scale over 2 to 3 weeks is the real test.
- Not for under 18s, pregnancy or breastfeeding, or anyone with a history of disordered eating. Talk to your GP.
- Very low energy diets are a medical treatment. Do them only with your doctor.
Sources
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 11:20, 2014.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet 378(9793):826 to 837, 2011.
- Wishnofsky M. Caloric equivalents of gained or lost weight. American Journal of Clinical Nutrition 6(5):542 to 546, 1958.