A calorie deficit means eating fewer calories than your body burns (your TDEE), so it draws on stored energy and body weight falls. To calculate yours: find your TDEE, then subtract 10–25%, or a fixed 250–750 kcal. A 500 kcal daily deficit is about 1 lb (0.45 kg) of loss per week in the short term, though the pace slows as you lose weight.
Key takeaways
- Deficit = TDEE minus calories eaten; for a 35-year-old woman with a TDEE of 2,239, eating 1,739 is a 500 kcal (22%) deficit.
- A percentage deficit (10–25% of TDEE) scales to body size better than a fixed 500 kcal.
- The 500 kcal = 1 lb per week rule works for a few weeks and then overstates loss as your TDEE falls.
- If the scale is flat in a deficit, check logging accuracy, activity assumptions and time window before cutting calories further.
- Never plan a deficit that puts you below BMR or below 1,200 kcal (women) or 1,500 kcal (men) without medical supervision.
Want your own number? The calorie deficit calculator sets a daily target and estimates your goal date. This guide explains what a deficit is and how to use one well.
What is a calorie deficit?
A calorie deficit is the gap between the calories you burn and the calories you eat. Your burn is your TDEE (see what TDEE is). When intake falls below it, the body covers the gap from stored energy, mostly body fat, and weight trends down.
deficit (kcal) = TDEE − calories eaten deficit (%) = deficit ÷ TDEE × 100 daily target = TDEE × (1 − deficit %)
How do you calculate a calorie deficit?
- Find your TDEE, for example with the TDEE calculator. The standard method is Mifflin–St Jeor BMR times an activity factor (Mifflin et al., 1990).
- Choose a deficit: 10–20% for most people.
- Subtract it. That is your daily target.
- Check the target stays above your BMR and the minimum floors below.
Worked example
Our example woman (35, 5′5″, 165 lb, moderately active) has a TDEE of 2,239 kcal and a BMR of 1,444 kcal.
| Daily deficit | % of TDEE | Daily target | Expected loss (short term) | Above BMR? |
|---|---|---|---|---|
| 250 kcal | 11% | 1,989 | 0.5 lb/week | Yes |
| 500 kcal | 22% | 1,739 | 1 lb/week | Yes |
| 750 kcal | 34% | 1,489 | 1.5 lb/week | Barely (45 kcal) |
| 1,000 kcal | 45% | 1,239 | 2 lb/week | No |
Expected loss uses 3,500 kcal per pound, which is a short-term approximation. The man in our other example (30, 5′10″, 190 lb, TDEE 2,834) would need a 500 kcal deficit to eat 2,334 kcal, which is only 18% of his TDEE.
How much of a deficit is a 500 calorie deficit?
A 500 kcal daily deficit adds up to 3,500 kcal a week, the energy in about a pound of body fat by the classic rule. That makes it a popular target. Its flaws are that it is a fixed number, a bigger bite out of smaller people’s intake, and that the 1 lb-a-week prediction does not hold for months (Hall et al., 2011; Thomas et al., 2014). Read why in how many calories are in a pound of fat.
Why am I not losing weight in a calorie deficit?
If your scale is flat after three weeks, the cause is rarely a “broken metabolism”. Check these in order.
- Your deficit is smaller than you think. TDEE estimates can be 10% off, and the biggest source of error is activity level. A woman whose true TDEE is 2,000 rather than 2,239 has a deficit of 97 rather than 336 kcal at a 1,903 target.
- Intake is under-logged. Oils, drinks, bites and weekend meals add up fast.
- The time window is too short. Water retention can hide fat loss for a couple of weeks. Compare weekly averages, not single days (Turicchi et al., 2020).
- Your TDEE has dropped. A lighter body burns less, and during dieting some people also move less without noticing. Expenditure can fall a little more than body size predicts (Rosenbaum & Leibel, 2010).
- You have reached maintenance. The deficit has shrunk to nothing.
The remedy is data, not a harsher diet: log for 2–3 weeks, compute your real maintenance with an adaptive TDEE calculator, then reset your target. For more help see weight loss plateaus.
Should the deficit come from food, movement or both?
Both work, and the best split is the one you can keep up. Food is usually the bigger lever because it is easier to cut 300 kcal than to burn it. Movement adds a smaller amount but also supports health and muscle.
For our example woman, adding 5,000 steps at a brisk pace (about 2.1 miles, 36 minutes) burns roughly 149 kcal above resting, using her height and weight. A 500 kcal deficit could therefore be about 350 kcal less food plus those extra steps. Try the steps to calories calculator for your numbers.
Be careful with the “eat back your exercise” habit. Fitness trackers often over-report; see how accurate calorie estimates are. If you already chose an activity factor that includes your workouts, they are in your TDEE and should not be counted twice.
Deficit safety and floors
A moderate deficit also leaves room for adequate protein; see how much protein you need.
Frequently asked questions
How big should my calorie deficit be?
For most people, 10–20% below TDEE: big enough to see weekly progress, small enough to keep protein, training and energy intact. For a TDEE of 2,239 kcal that is 1,791–2,015 kcal. Smaller deficits suit lean people near their goal, and larger ones suit people with a lot to lose, for short periods.
Is a 500 calorie deficit good?
For many people, yes. It equals roughly 1 lb (0.45 kg) a week by the 3,500-calorie rule, and is 18–22% of TDEE for our example man and woman. It is aggressive for small or sedentary people, whose TDEE may be near 1,800 kcal. Check it against your own TDEE with the calorie deficit calculator.
How many calories should I eat in a deficit?
Your TDEE minus the deficit. A woman with TDEE 2,239 eats about 1,903 kcal at 15%; a man with TDEE 2,834 eats about 2,408 at 15%. See the full table in how many calories to eat. Never plan below your BMR without medical supervision.
Can you lose weight without counting calories?
Yes, because many habits create a deficit indirectly: more protein and fiber, fewer liquid calories, and more walking. But weight still follows energy balance. Counting for a few weeks is useful for learning portion sizes and for diagnosing a stalled trend.
How long can I stay in a calorie deficit?
There is no fixed limit, but deficits get harder over time as hunger rises and TDEE falls. Some people plan a phase of several weeks followed by maintenance weeks. See diet breaks and refeeds for the evidence, and consider a doctor's guidance for long or large deficits.
Is it OK to have a 1,000 calorie deficit?
It is too large for many people. For our example woman it is a 45% deficit and drops her intake to 1,239 kcal, below her BMR of 1,444. Only people with much higher TDEEs, such as larger or very active adults, can do it without going under BMR, and it should be supervised.
References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2):241–247.
- Hall KD, Sacks G, Chandramohan D, et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet 378(9793):826–837.
- Thomas DM, Gonzalez MC, Pereira AZ, Redman LM, Heymsfield SB (2014). Time to correctly predict the amount of weight loss with dieting. Journal of the Academy of Nutrition and Dietetics 114(6):857–861.
- Turicchi J, O’Driscoll R, Horgan G, et al. (2020). Weekly, seasonal and holiday body weight fluctuation patterns among individuals engaged in a European multi-centre behavioural weight loss maintenance intervention. PLOS ONE 15(4):e0232152.
- Rosenbaum M, Leibel RL (2010). Adaptive thermogenesis in humans. International Journal of Obesity 34(Suppl 1):S47–S55.