Weight Loss Calculator

Your body weight changes when the calories you eat and the calories you burn don't match. Eat less than your daily burn (TDEE) and you lose weight; eat more and you gain. A common rule is that about 7,700 kcal of food energy equals 1 kg of body weight (about 3,500 kcal per lb), so a steady gap of 550 kcal a day comes to about 0.5 kg a week.

Your daily burn depends on your weight, so it falls as you get lighter. This calculator works the plan out day by day: each day it finds your burn at that day's weight and takes the gap from it. Planning by pace keeps the gap the same, so the calories to eat step down a little each week. Planning by date or by what you'll eat keeps one daily figure, so progress slows near the end. Switch the falling burn off in Advanced to see the simple 7,700 rule most calculators use.

The formula

BMR (Mifflin–St Jeor) = 10 × weight in kg + 6.25 × height in cm − 5 × age, then + 5 for men or − 161 for women
Daily burn (TDEE) = BMR × activity factor + extra exercise
Daily gap = kg a week × 7,700 ÷ 7
Calories to eat = daily burn − gap (to lose) or + gap (to gain)
Days to goal = kg to lose × 7,700 ÷ daily gap
Each day: weight change = (calories eaten − burn at today's weight) ÷ 7,700

Worked example

A 30-year-old woman, 165 cm tall, weighing 75 kg with light exercise, wants to reach 67 kg at 0.5 kg a week. BMR = 10 × 75 + 6.25 × 165 − 5 × 30 − 161 = 750 + 1,031.25 − 150 − 161 = 1,470.25 kcal. Daily burn = 1,470.25 × 1.375 = 2,021.59 kcal. The gap is 0.5 × 7,700 ÷ 7 = 550 kcal a day, so she eats 2,021.59 − 550 = 1,471.59, about 1,470 kcal a day (about 6,157 kJ) to start.

She has 75 − 67 = 8 kg to lose: 8 × 7,700 ÷ 550 = 112 days, or 16 weeks. That's 0.5 ÷ 75 = 0.67% of her weight a week, inside the common 1% guide. Each 1 kg lost lowers her burn by 10 × 1.375 = 13.75 kcal, so in week 2 she eats 6.875 kcal less, and in the last week (starting at 67.5 kg) about 2,021.59 − 7.5 × 13.75 − 550 = 1,368.47 kcal. At 67 kg her BMR is 1,390.25 kcal, so the calories to keep her new weight are 1,390.25 × 1.375 = about 1,912 kcal a day. Her BMI goes from 75 ÷ 1.65² = 27.5 to 67 ÷ 1.65² = 24.6.

If she ate a fixed 1,470 kcal every day instead, her gap would shrink as she got lighter, and the goal would take longer than 16 weeks. Plan by "Calories I'll eat" in Advanced to see how much longer.

Paces at a glance

Common guidance used

• Pace: about 0.5 to 1 kg (1 to 2 lb) a week, and not more than about 1% of your body weight a week. Slower is often easier to keep up.
• Calorie floor: not under about 1,200 kcal a day for women or 1,500 kcal for men without medical supervision, because it gets hard to get enough nutrients. When a plan would go lower, this calculator holds the floor and shows the later date.
• Goal weight: a BMI under 18.5 is below the healthy range. The calculator flags goals below it.
• Weight gain: a gentle surplus of about 0.25 to 0.5 kg a week, with strength training, tends to add more muscle and less fat than a big surplus.

Why real results differ

Early weight loss is often faster because of water and stored carbohydrate, and weight swings by a kilo or more from day to day. The 7,700 kcal rule is a rough average; your body may also adapt a little more than this model shows. Use your weekly average weight, not one weigh-in, and adjust by 100 to 200 kcal if progress is much faster or slower than the plan. For your daily burn on its own see the TDEE calculator, and for protein targets the macro calculator.

This is general information for healthy adults, not medical advice. Talk to a doctor or registered dietitian before losing a lot of weight, if you have a health condition or take medicines, or if you are pregnant or breastfeeding. If you're worried about your eating, please reach out to a doctor or an eating disorder helpline.