Calorie Deficit Calculator
Enter your details, goal weight and either a weekly loss rate or a target date to get a daily calorie target, the deficit behind it and a projected weight curve, with built-in safety limits.
Projected weight
Milestones
| Week | Date | Projected weight | Lost so far |
|---|
Estimates use about 7,700 kcal per kg (3,500 kcal per lb) of body weight. Real weight loss is not perfectly linear: water shifts cause day-to-day swings and your maintenance calories fall as you get lighter, so recalculate every few weeks. This tool is for general information, not medical advice. Talk to a doctor before a large deficit, if you are pregnant or breastfeeding, under 18, or have a medical condition or a history of disordered eating.
How to use the Calorie Deficit Calculator
- Choose your sex and units, then enter your age, height and current weight.
- Enter your goal weight and pick the activity level that matches a typical week.
- Plan by weekly rate (0.5 kg or 1 lb a week is a good default) or switch to Target date and pick a date.
- Press Calculate to see your daily calorie target, deficit, goal date and projected weight curve.
- Read any warnings: the calculator slows plans that are too aggressive and never goes below a safe minimum intake.
How the calorie target is calculated
- BMR (Mifflin-St Jeor): men 10W + 6.25H − 5A + 5; women 10W + 6.25H − 5A − 161 (W in kg, H in cm, A in years).
- TDEE = BMR × activity factor.
- Daily deficit = weekly loss (kg) × 7,700 ÷ 7, or weekly loss (lb) × 3,500 ÷ 7.
- Calorie target = TDEE − daily deficit, never below 1,200 kcal (women) or 1,500 kcal (men).
- Time to goal = weight to lose × 7,700 ÷ daily deficit, in days.
Worked example
A 30-year-old man, 180 cm and 90 kg, moderately active, wants to reach 80 kg at 0.5 kg a week.
- BMR = 10 × 90 + 6.25 × 180 − 5 × 30 + 5 = 1,880 kcal.
- TDEE = 1,880 × 1.55 = 2,914 kcal.
- Deficit = 0.5 × 7,700 ÷ 7 = 550 kcal a day, so the target is 2,364 kcal a day.
- Time to goal = 10 × 7,700 ÷ 550 = 140 days (20 weeks).
Activity levels and weekly loss rates
| Activity level | Factor | Weekly loss | Daily deficit |
|---|---|---|---|
| Sedentary | 1.2 | 0.25 kg (0.5 lb) | ≈ 275 kcal |
| Lightly active | 1.375 | 0.5 kg (1.1 lb) | ≈ 550 kcal |
| Moderately active | 1.55 | 0.75 kg (1.65 lb) | ≈ 825 kcal |
| Very active | 1.725 | 1 kg (2.2 lb) | ≈ 1,100 kcal |
| Extra active | 1.9 | Rates above about 1% of body weight a week are capped by the calculator | |
Frequently asked questions
How many calories should I eat to lose weight?
Start from your maintenance calories (TDEE) and subtract a daily deficit. A deficit of about 550 kcal a day leads to roughly 0.5 kg (1.1 lb) of loss per week, because one kilogram of body fat stores about 7,700 kcal. The calculator does this for your exact numbers.
What is a safe calorie deficit?
For most adults a deficit that produces 0.5 to 1% of body weight loss per week is considered safe and sustainable, usually 300 to 750 kcal a day. Women are generally advised not to eat under 1,200 kcal and men under 1,500 kcal a day without medical supervision.
How is BMR calculated?
This tool uses the Mifflin-St Jeor equation: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. TDEE is BMR multiplied by an activity factor from 1.2 (sedentary) to 1.9 (extra active).
How is the calorie target worked out from a target date?
The calculator divides the weight you need to lose by the days until your date to get a weekly rate. If that rate is faster than about 1% of your body weight per week, it uses the safe maximum and shows the later date you can realistically expect.
Why is my weight loss slower than predicted?
Water retention, hormones and the scale's daily swings hide fat loss for a week or two at a time. Your maintenance calories also fall as you lose weight. Look at the weekly average and recalculate your target every 4 to 6 weeks.
Is 3,500 calories really one pound?
It is a useful approximation for planning. One pound of body fat holds about 3,500 kcal (7,700 kcal per kg). Actual loss varies because early weight loss includes water and glycogen, and the body adapts over time.
Who should not use a calorie deficit calculator?
People who are pregnant or breastfeeding, under 18, have diabetes or another medical condition, or have a history of disordered eating should talk to a doctor or registered dietitian instead of following an automated target.