Calorie deficit calculator — how long to reach your ideal weight
Enter your details and a goal weight — for example, the ideal weight for your height. The calculator estimates your daily energy needs with the Mifflin–St Jeor equation, sets a calorie target for the pace you choose and shows when you can expect to reach the goal.
How the calculation works
1. Resting energy (BMR). Mifflin–St Jeor: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men or − 161 for women.
2. Daily needs (TDEE). BMR is multiplied by an activity factor from 1.2 (sedentary) to 1.9 (very active).
3. Deficit and timeline. About 7,700 kcal corresponds to 1 kg of body fat, so losing 0.5 kg a week needs a deficit of roughly 550 kcal a day. The plan never goes below 1,200 kcal (women) or 1,500 kcal (men) a day. In reality weight loss slows down over time, so treat the date as an optimistic estimate.
Frequently asked questions
What is a safe calorie deficit?
For most adults, a deficit of 500–750 kcal a day (about 0.5–0.75 kg or 1–1.5 lb a week) is a common, sustainable range. Larger deficits make it harder to keep muscle and get enough nutrients.
Why is my weight loss slower than the calculator predicts?
As you lose weight your body needs less energy, and water shifts hide fat loss from week to week. Recalculate every 4–6 weeks with your new weight.
Which goal weight should I choose?
Any weight within the healthy BMI range (18.5–24.9) for your height is reasonable. The ideal-weight formulas give a single reference point inside that range.
Is this calculator suitable for everyone?
No. It is not designed for pregnancy, breastfeeding, people under 18, or people with medical conditions that affect weight — ask a doctor or dietitian for a personal plan.
