Calorie Deficit CalculatorFind Your Deficit & Goal Weight Date
Choose a deficit and goal weight to see how many calories to eat, the realistic date you’ll reach your goal, and a week-by-week projection that allows for your metabolism slowing as you lose weight.
Built & medically reviewed by Manzoor Ahmad, Pharmacist & Calculator Developer · Updated
Projection logic follows the adaptive energy-balance research behind the NIH Body Weight Planner. BMR uses the Mifflin-St Jeor equation.
How do you calculate a calorie deficit?
Work out your maintenance calories (TDEE), then subtract 250–1,000 calories a day. A 500-calorie daily deficit leads to about 1 lb (0.45 kg) of loss a week at first. Weight loss slows as you get lighter, because your maintenance falls too. Never go below about 1,200 calories a day for women or 1,500 for men without medical supervision.
Plan your deficit
feet · inches
kcal below your maintenance each day
Feb 14, 2027
Eat 1,625 kcal/day (a 500 kcal deficit) for about 15 weeks to lose 13 lb.
Your weight projection
The solid line recalculates your burn every week as you get lighter. The dashed line is the simple “3,500 kcal = 1 lb” rule, which is usually too optimistic.
Milestones
Calorie deficit sizes compared
Bigger isn’t better. The best deficit is the one you can keep up while protecting muscle, sleep and training.
| Daily deficit | Expected loss / week | Best for | Trade-offs |
|---|---|---|---|
| −250 kcal | ≈ 0.5 lb (0.23 kg) | Lean people, the last 10 lb, slow cuts | Slow. Progress is hard to see on the scale |
| −500 kcal | ≈ 1 lb (0.45 kg) | Most people. The standard recommendation | Moderate hunger. Very sustainable |
| −750 kcal | ≈ 1.5 lb (0.7 kg) | People with 30+ lb to lose | Needs high protein and good sleep |
| −1,000 kcal | ≈ 2 lb (0.9 kg) | Short phases, higher body weight | More muscle loss, fatigue and rebound risk |
Why our goal date is more honest
Most deficit calculators divide the weight you want to lose by a fixed weekly rate. That ignores the fact that a lighter body burns fewer calories. Our engine recalculates your Mifflin-St Jeor maintenance every week at your new projected weight. Your fixed intake therefore creates a slightly smaller deficit as you go. This matches the NIH Body Weight Planner’s finding that weight loss slows down over time.
143 lb → 130 lb at a 500 kcal deficit
- Maintenance today: 2,125 kcal (woman, 30, 5’5″, moderately active)
- Fixed intake: 1,625 kcal/day
- The simple 3,500 rule predicts 13 lb in 13 weeks.
- The adaptive model predicts about 15 weeks, because by 130 lb her maintenance has fallen to about 2,030 kcal.
- After reaching her goal, she should eat about 2,030 kcal, not the 2,125 she maintained on before.
5 rules for a deficit that works
- Protein first: 1.6–2.2 g per kg of body weight keeps hunger down and muscle on.
- Lift 2–3 times a week: it signals your body to hold onto lean mass.
- Keep your steps up: daily movement (NEAT) quietly drops during diets. Aim for 7,000–10,000 steps.
- Plan diet breaks: 1–2 weeks at maintenance every 8–12 weeks helps you stick with it.
- Exit slowly: raise your calories by 100–150 a week until you reach your new maintenance.
Dieting while on medication
A calorie deficit can change how some medicines behave. People with diabetes on insulin or sulfonylureas (such as glimepiride and gliclazide) are at risk of hypoglycaemia when they eat less, so their doses often need lowering. Talk to your doctor before you start. People on blood-pressure tablets may find their readings fall as they lose weight, and dizziness on standing is a sign to get them checked.
Be careful with “fat-burner” supplements as well. Many contain high-dose caffeine, synephrine or yohimbine, which can raise heart rate and blood pressure and interact with antidepressants and stimulant medications.
Related calculators
Calorie Deficit calculator FAQs
A calorie deficit means eating fewer calories than your body burns (your TDEE). Your body makes up the shortfall from stored energy, mainly fat. A daily deficit of about 500 calories leads to roughly 1 lb (0.45 kg) of weight loss a week at first.
For most people, 300–500 calories a day below maintenance, about 15–25%, is the sweet spot for steady fat loss without losing much muscle. People with more weight to lose can use 750–1,000 calories a day for limited periods.
At a 500-calorie daily deficit, losing 10 lb takes about 10–12 weeks. At 1,000 calories a day, it takes about 5–6 weeks. The last few pounds take longer, because your maintenance calories fall as your weight drops.
The usual causes are underestimating what you eat, overestimating your activity level, and water retention from new exercise, salty meals or your menstrual cycle hiding fat loss. Compare 2-week averages, not single days. Only reduce your intake by 100–200 calories if the trend stays flat for 3 weeks or more.
A 1,000-calorie daily deficit can be safe for people with plenty of weight to lose, as long as total intake stays above 1,200 calories (women) or 1,500 (men) and protein is high. For leaner people it causes more muscle loss, fatigue and rebound, so a smaller deficit works better.
Mostly fat, if you eat enough protein (1.6–2.2 g/kg), do resistance training, and avoid very large deficits. Without those, up to a quarter of the weight lost can come from lean tissue.
No. Counting is the most precise way, but higher-protein meals, more vegetables, fewer liquid calories and more daily steps can create a deficit without tracking. Use this calculator to set a target, then check that your weekly weight trend matches it.
Eat at your new maintenance level, which is lower than before because a lighter body burns less. Raise your intake gradually, by 100–150 calories a week, from your diet calories up to the ‘maintenance at goal’ figure the calculator shows.
Manzoor Ahmad
Pharmacist · Supplement & Nutrition Writer (9+ yrs) · Calculator Developer (13+ yrs)
I’m a practising pharmacist and I build DexoCalc’s calculators. Most deficit calculators promise dates you won’t hit, because they ignore metabolic slowdown. I built this one to recalculate every week, and to flag the medicines, such as diabetes drugs and fat burners, that I see cause problems for dieters.
References
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–837. PubMed
- NIDDK. Body Weight Planner.
- Mifflin MD, et al. Am J Clin Nutr. 1990;51(2):241–247. PubMed
- Helms ER, et al. A systematic review of dietary protein during caloric restriction in resistance-trained lean athletes. Int J Sport Nutr Exerc Metab. 2014;24(2):127–138. PubMed
- CDC. Losing Weight.
Medical disclaimer: Projections are estimates for healthy adults and are not medical advice. Do not use calorie restriction if you are pregnant, breastfeeding, under 18 or have a history of disordered eating. If you take medicine for diabetes or blood pressure, talk to your doctor before starting a deficit.