Calorie deficit calculator: calories for weight loss
Pick a weekly pace and get a daily calorie target, a time-to-goal estimate, and a warning when the plan gets too aggressive. Built on Mifflin-St Jeor.
How many calories should I eat to lose weight?
Eat below your maintenance calories, or TDEE. A pace of 0.5 kg (about 1 lb) a week needs a deficit of roughly 550 kcal a day, based on the common estimate of 7,700 kcal per kg of body fat. A 30-year-old woman, 168 cm and 68 kg, who exercises lightly maintains on about 1,950 kcal, so her target is about 1,400 kcal.
How to use the calculator
- Enter your body and activityFill in sex, age, height and weight, then pick your activity level. The calculator starts at Light, exercise 1–3 days a week.
- Choose a pacePick 0.25, 0.5, 0.75 or 1 kg a week, or 0.5 to 2 lb in US units. A slower pace gives a higher daily target.
- Add a goal weight if you have oneThe optional goal weight adds a time-to-goal estimate in weeks. It only appears when the goal is below your current weight.
- Read the target and any warningThe big number is what to eat each day, rounded to the nearest 10 kcal. A warning appears if the target is under a common floor or the pace is fast for your size.
A calorie deficit means eating less energy than you burn. Your body makes up the gap from its stores, mostly fat if you eat enough protein and keep lifting. This calculator works backwards from a pace. You choose how fast you want the scale to move, and it tells you how far under maintenance that puts you. For the background, read how a calorie deficit works.
The formula
Maintenance comes from the same math as the TDEE calculator. The deficit comes from your pace. The target is one minus the other.
- Maintenance: TDEE = Mifflin-St Jeor BMR × activity factor
- Daily deficit: pace (kg per week) × 7,700 ÷ 7
- Target: TDEE − daily deficit, each rounded to the nearest 10 kcal first so the rows add up
- Time to goal: (current weight − goal weight) ÷ pace, rounded up to whole weeks
US paces are converted to kilograms first, so 1 lb a week is 0.4536 kg and a daily deficit of about 500 kcal.
The pace options
| Pace per week | Daily deficit | Target (example) | Warning shown |
|---|---|---|---|
| 0.25 kg | 280 kcal | 1,670 kcal | None |
| 0.5 kg | 550 kcal | 1,400 kcal | None |
| 0.75 kg | 830 kcal | 1,120 kcal | Under 1,200 kcal |
| 1 kg | 1,100 kcal | 850 kcal | Under 1,200 kcal |
The example is the calculator’s default person: a woman of 30, 168 cm and 68 kg, at Light activity, with a maintenance of 1,950 kcal. In US units the paces are 0.5, 1, 1.5 and 2 lb, with deficits of about 250, 500, 750 and 1,000 kcal.
A worked example
She weighs 68 kg and enters a goal of 62 kg at 0.5 kg a week. Her BMR is 1,419 kcal. Light activity multiplies it by 1.375, for a maintenance of 1,951 kcal, shown as 1,950. The deficit is 0.5 × 7,700 ÷ 7 = 550 kcal. Her target is 1,950 − 550 = 1,400 kcal. The gap to goal is 6 kg, and 6 ÷ 0.5 = 12, so the calculator says about 12 weeks.
If she switches to 0.75 kg a week, the target falls to 1,120 kcal and she sees a warning that it is under 1,200 kcal a day. At 0.25 kg a week she eats 1,670 kcal, and the estimate stretches to 24 weeks.
The warnings, and why they’re there
- Under the floor: If the target is under 1,200 kcal a day for women or 1,500 kcal for men, the calculator suggests a slower pace, more movement, or planning it with a dietitian or doctor. These floors are widely used rules of thumb, not physiology. Below them it gets hard to eat enough protein, fiber and micronutrients.
- Pace over 1% of body weight: If your weekly pace is more than 1% of your body weight, you see a note that slower is easier to hold and keeps more muscle. Reviews of dieting lifters, including Helms and colleagues (2014), point to 0.5–1% a week. For a 68 kg person the line is 0.68 kg.
Only one warning shows at a time, and the floor comes first. At 0.75 kg a week the default person trips both, but she sees the floor warning.
How accurate is the time-to-goal estimate?
It is a straight line, and real weight change isn’t. Three things bend it.
- The 7,700 figure: It is an approximation for a kilogram of body fat. Early weeks include water and stored carbohydrate, so they often move faster than the math.
- A shrinking body: As you get lighter, your maintenance falls, and the same intake makes a smaller deficit. Work by Kevin Hall at the NIH showed the simple rule overestimates loss over months for this reason.
- Daily noise: Salt, a hard session or a menstrual cycle can move the scale by a kilogram or more overnight. Compare weekly averages.
So re-run the calculator every few kilograms. Read the weeks figure as a rough horizon, not a deadline.
What to do with the target
A target works if you hit it most days and can see whether it is working. Log your weight a few times a week in a weight tracker and judge by the trend. Keep protein high while you eat less; the protein calculator has a range for lifting in a deficit. FORM sets its own calorie targets with the same Mifflin-St Jeor equation × an activity factor, caps the weekly pace relative to your body weight, and lets you edit the number when your trend disagrees.
FAQ
Is a 1,200 calorie diet safe?
It is a common floor for women, not a goal. Below it, eating enough protein, fiber and micronutrients gets hard. If a plan takes you under 1,200 kcal a day, or 1,500 for men, plan it with a dietitian or doctor.
How fast should I lose weight?
Many health services suggest 0.5–1 kg (1–2 lb) a week at most. If you lift and want to keep muscle, 0.5–1% of your body weight a week is a common target.
Why am I not losing weight in a calorie deficit?
Usually the intake or the burn estimate is off: portions drift and activity levels get rated too high. Water can also hide fat loss for a week or two. Log carefully for two weeks, then lower the target by 100–200 kcal if the average hasn’t moved.
Does the calculator adjust as my weight drops?
No. It uses your current weight for the whole estimate. Re-run it every few kilograms so the target keeps up with your new maintenance.
What does 7,700 calories per kilogram mean?
It is the planning figure for the energy in a kilogram of body fat, about 3,500 kcal per pound. It is an approximation, and it overstates loss over long stretches because your burn drops as you get lighter.