Calorie Deficit Calculator
Turn a weekly weight-loss goal into a daily target, with a safety floor.
| Maintenance (TDEE) | 2,662 kcal/day activity: Moderately active |
|---|---|
| Daily calorie deficit | 500 kcal/day 1 lb per week |
| Target intake | 2,162 kcal/day |
| Weekly loss | 1 lb (0.5 kg) if you hit the target every day |
| Time to lose 10 lb | 10 weeks |
Based on 3,500 kcal per pound; individual results move with water, adherence and training.
What a calorie deficit is
A calorie deficit is the gap between the energy you burn and the energy you eat. If you burn 2,600 kcal a day and eat 2,100, you are running a 500 kcal deficit, and a week of that adds up to 3,500 kcal - the number usually quoted for a pound of body weight. The arithmetic is simple; what makes it hard in practice is that both sides of the equation move.
Two details decide whether a deficit works. The first is size: a deficit large enough to see progress in a fortnight but small enough that you can train, sleep and stay consistent. The second is duration: a deficit is a phase with a start and an end, not a permanent way of eating. Most people get better results from a moderate deficit held for eight to sixteen weeks than an aggressive one abandoned after ten days.
| Daily deficit | Weekly energy | Expected weekly loss |
|---|---|---|
| 250 kcal | 1,750 kcal | about 0.5 lb (0.23 kg) |
| 500 kcal | 3,500 kcal | about 1 lb (0.45 kg) |
| 750 kcal | 5,250 kcal | about 1.5 lb (0.68 kg) |
| 1,000 kcal | 7,000 kcal | about 2 lb (0.91 kg) |
| 1,500 kcal | 10,500 kcal | about 3 lb (1.36 kg), rarely sustainable |
How the calculator builds your target
The calculator starts from your total daily energy expenditure, which it derives from the Mifflin-St Jeor equation and the activity level you choose, and then subtracts the deficit implied by your weekly goal. One pound of fat is treated as 3,500 kcal, so a goal of one pound a week means a 500 kcal daily deficit; half a pound a week means 250 kcal.
Two guardrails are applied on top. First, the target never drops below a floor of 1,500 kcal for men and 1,200 kcal for women, because below that it becomes difficult to cover protein, micronutrient and training needs without supervision. Second, the page tells you how long the goal will take, so a target that needs six months is visible as a six-month plan rather than a surprise.
Reading your deficit result
The result table gives you four figures: your maintenance calories, the daily deficit your goal implies, the intake you should aim for, and the pace that intake represents. The last row warns you if the maths has pushed you under the safety floor - if it has, the answer is not to eat less but to extend the timeframe.
The projected weekly loss is an average, not a schedule. Bodies do not release weight in a straight line: sodium, carbohydrate stores, hormonal cycle and training load all swing the scale by one to two kilograms without any change in fat. Judge the plan on a two-to-three week rolling average, never on the difference between two mornings.
What is a sustainable rate of loss?
Guidance from public health bodies converges on roughly 0.5 to 1 kg (1 to 2 lb) a week, and the sports nutrition literature adds a useful refinement: staying under about 1% of body weight per week protects lean mass, training performance and hormonal health. For a 75 kg person, 1% is 750 g - so a 1 kg weekly loss is at the top of the sensible range, not the middle.
Lighter people have less room. Someone at 60 kg aiming for 1 kg a week is trying to lose 1.7% of their body weight every week, which is why the same plan that worked at 90 kg often fails at 65 kg. When progress stalls, the fix is usually a smaller deficit plus more movement, not a steeper one.
| Body weight | 1% per week | Typical intake the deficit implies |
|---|---|---|
| 60 kg (132 lb) | 0.6 kg (1.3 lb) | a 660 kcal daily deficit |
| 75 kg (165 lb) | 0.75 kg (1.65 lb) | a 825 kcal daily deficit |
| 90 kg (198 lb) | 0.9 kg (2.0 lb) | a 990 kcal daily deficit |
| 105 kg (231 lb) | 1.05 kg (2.3 lb) | a 1,155 kcal daily deficit |
Why the scale stalls even when the maths is right
Weight loss is never linear, and the reasons are mundane. A high-carbohydrate day adds 300 to 500 g of water bound to glycogen. A salty meal adds fluid. A hard training session causes temporary inflammation and swelling. Menstrual-cycle water retention can add one to two kilograms for several days. None of that is fat, and all of it will show up if you weigh yourself once and panic.
The other common cause is measurement drift rather than metabolic damage: portions estimated generously, cooking oil ignored, weekend days not logged, or drinks forgotten. Before cutting calories further, spend a week weighing food honestly. It frequently explains a stall that a bigger deficit would not fix.
A worked example
A 30-year-old man at 178 cm and 75 kg with moderate activity has a maintenance figure of about 2,662 kcal. Aiming to lose one pound a week sets a 500 kcal daily deficit, so his target intake is about 2,160 kcal - comfortably above the 1,500 kcal floor, and roughly a 19% reduction.
The same person choosing half a pound a week would eat about 2,410 kcal, and ten pounds would take twenty weeks. Switching to two pounds a week pushes intake to about 1,660 kcal, only just above the floor and under a 1.5% weekly loss rate - a plan worth discussing with a clinician rather than simply starting.
Frequently asked questions
Is a 1,200 calorie diet safe?
For most adults it is the bottom of the range rather than a target to aim for, and it rarely fits anyone over about 60 kg without losing muscle. Use the intake the calculator gives you; if it has hit the floor, lengthen the timeframe instead of cutting further.
How long should I stay in a deficit?
Eight to sixteen weeks is the usual working range, followed by a maintenance phase of similar length. Long deficits erode adherence, training quality and lean mass, and the maintenance phase is what makes the loss stick.
Can I create the deficit with exercise only?
You can, but it is inefficient: an hour of running is roughly 600 kcal, or about one sandwich. Most sustainable plans use food for the bulk of the deficit and exercise to protect muscle and raise daily burn.
Why does my weight go up after a hard workout?
Muscle repair draws in fluid and glycogen, so the scale can rise for a day or two after heavy or unfamiliar training. That is water, not fat, and it resolves on its own.
Should I eat more on training days?
The activity level already averages your training week, so keep intake stable unless the session was unusually long. If you prefer cycling calories, hold the weekly total and shift 100 to 200 kcal toward training days.
What happens if I eat under the floor for weeks?
Expect fatigue, poor recovery, loss of strength and menstrual disruption, plus a higher chance of rebound. Intakes below about 1,200 kcal should be supervised by a clinician or dietitian.
Sources
- Dietary Guidelines for Americans
- NHLBI: Losing weight
- NHS: Healthy weight
- Mifflin MD et al., predictive equation for resting energy expenditure
Formulas and thresholds are taken from the sources above. They are a starting point for adults, not a diagnosis.
Last reviewed September 12, 2026. How we calculate · Editorial policy