Calorie Deficit Calculator
Daily calories to reach a goal weight by a set date. Runs in your browser.
About this calorie deficit calculator
This calorie deficit calculator tells you how many calories to eat each day to reach a goal weight by a date you choose. Enter your current weight, goal weight and deadline, and it works out the daily deficit, your calorie target and how fast that is per week.
It also checks whether the plan is safe. You get a warning if the target drops under 1,200 kcal for women or 1,500 kcal for men, if you would lose more than 1% of your body weight a week, or if the goal weight is below a healthy BMI.
Prefer to pick a pace instead? Switch to weekly rate and it gives you the date. Either way you get a month-by-month table that lowers the target as your weight drops, which is the part most plans leave out.
Features
Goal date or weekly rate
Set a deadline and get the deficit, or choose 0.25 to 1 kg (0.5 to 2 lb) a week and get the date.
Safe-rate warnings
Flags a target under the usual minimum intake, a pace over 1% of body weight a week, a deficit over 1,000 kcal, and a goal BMI under 18.5.
Maintenance now and at goal
Your TDEE today from Mifflin-St Jeor and your activity level, plus what it will be at the goal weight, so you know what to eat once you get there.
Projection chart
The planned straight line against what happens if you eat the same calories the whole time. The gap shows why progress slows.
Monthly checkpoints
Every four weeks: expected weight, new maintenance and the adjusted calorie target that keeps the deficit the same.
Use your real maintenance
If months of food logging tell you your true maintenance, enter it and the plan uses that instead of the formula.
How to use the calorie deficit calculator
- 1Enter sex, age, height, current weight, goal weight and activity level.
- 2Choose a goal date, or a weekly rate to get the date instead.
- 3Read your daily target, warnings and the month-by-month plan.
When to use it
A wedding or holiday deadline
Enter the date and see straight away whether the goal is realistic or needs a later date.
Checking an app's number
Diet apps often hand out a target without showing the maths. Here every step is written out with your figures.
Planning a slow gain
Set a goal above your current weight and it shows the daily surplus instead, with a note if it is more than about 500 kcal.
After a plateau
Re-enter your new weight. Your maintenance has dropped, so the old target is no longer a real deficit.
How do you calculate a calorie deficit?
Start with your maintenance calories (TDEE). This page uses the Mifflin-St Jeor equation for resting energy, 10 × kg + 6.25 × cm − 5 × age, plus 5 for men or minus 161 for women, then multiplies by an activity factor from 1.2 to 1.9. The BMI and TDEE calculator explains these activity levels in more depth.
Next, the weight gap. The common planning figure is about 7,700 kcal per kilogram of body weight (roughly 3,500 kcal per pound). Multiply the kilos to lose by 7,700 and divide by the days you have.
Worked example: a 35-year-old woman, 165 cm, 80 kg, lightly active. Her maintenance is about 2,056 kcal. To reach 70 kg in 20 weeks (140 days) she needs 10 × 7,700 ÷ 140 = 550 kcal a day less, so her target is about 1,506 kcal. That is 0.5 kg a week, or 0.6% of her body weight.
Why does weight loss slow down?
As you get lighter, you burn less. In the example above, maintenance at 70 kg is about 1,918 kcal, 138 kcal less than at the start. If she kept eating 1,506 kcal for all 20 weeks, the deficit would shrink each week and she would land near 71 kg on the goal date, not 70.
Research from the US National Institutes of Health (Hall and colleagues, The Lancet, 2011) showed that the simple 7,700 kcal rule overstates long-term loss for this reason. The checkpoint table fixes the simple version by lowering your target every four weeks so the deficit stays the same.
How fast is it safe to lose weight?
Health services commonly suggest about 0.5 to 1 kg (1 to 2 lb) a week. A useful personal limit is about 1% of your body weight a week. Past that, more of what you lose is muscle, hunger climbs and the plan rarely lasts.
- Deficit of 250 kcal a day: about 0.23 kg (0.5 lb) a week
- Deficit of 500 kcal a day: about 0.45 kg (1 lb) a week
- Deficit of 750 kcal a day: about 0.7 kg (1.5 lb) a week
- Deficit of 1,000 kcal a day: about 0.9 kg (2 lb) a week, the upper end for most people
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Input | Goal weight plus a date or a weekly rate | Fixed rates only |
| Safety checks | Minimum intake, 1% a week, large deficit, low goal BMI | One generic warning |
| Metabolic slowdown | Chart and monthly targets account for it | One flat number |
| Your own TDEE | Optional override | Formula only |
| Privacy | Weights stay in your browser | Often needs an account |
Tips
- Pick your activity level for an ordinary week. Most people choose one level too high.
- Expect the scale to bounce 1 to 2 kg from water. Judge progress on a weekly average, not one morning.
- Not sure what goal weight is realistic? Start with a healthy weight range for your height.
- Track your waist or body fat too. If the scale stalls but your waist shrinks, the plan is working.
- To count the exact days to a deadline, use the date difference calculator.
Questions
How many calories should I eat to lose weight?
Eat about 500 kcal less than your maintenance to lose roughly 0.5 kg (1 lb) a week. Enter your details and a goal date, and the calculator gives the exact target for you, plus a warning if it is too low.
Is a 1,000 calorie deficit safe?
It can be for people with a lot to lose and a high maintenance, but it is the upper limit for most. If it pushes you below 1,200 kcal (women) or 1,500 kcal (men), choose a later date.
How long will it take to lose 10 kg?
At 0.5 kg a week, about 20 weeks. At 0.75 kg a week, about 13 to 14 weeks. Switch to weekly rate in the calculator to see the exact date for your numbers.
Why am I not losing weight on a deficit?
Most often the real intake or activity differs from the estimate, or water retention is hiding fat loss. Formula maintenance can be off by 10% or more. Log carefully for two to three weeks before changing the plan.
Is 1 kg of fat really 7,700 calories?
It is a working average. Pure fat holds about 9 kcal per gram, but body fat tissue also contains water. Real loss also mixes in some lean tissue, so the figure is a planning estimate, not a law.
Should I eat back the calories I burn exercising?
Not if your activity level already includes that exercise. Choosing 'moderately active' and also eating back workout calories counts them twice.
What happens when I reach my goal?
Raise your intake to your new maintenance, shown as 'maintenance at goal weight'. It will be lower than your starting maintenance.
Is this medical advice?
No. It gives standard estimates for healthy adults. Speak to a doctor or dietitian first if you are pregnant, breastfeeding, under 18, or have diabetes, an eating disorder or another health condition.