Free weight-loss tool
Weight Loss Calculator
Start from the goal and the time you have, and work backwards: how many calories a day it takes, and whether that is a pace worth aiming for.
Worked example
For a 30-year-old man who weighs 75 kg and is 178 cm tall (lightly active), going from 75 kg to 70 kg in 12 weeks takes a deficit of about 458 kcal a day: eating about 1,904 kcal against a maintenance of 2,362 kcal.
Plan your weight loss
The result below starts from the example's numbers. Change any field and it updates as you type.
Track this target every day
Use the number above as your daily goal in CalorTracker, then log meals by photo, voice or text and see where your day stands against it. Free to start, no card needed to explore.
Results are estimates from published formulas, not medical advice. Your own body can sit above or below them.
Where the formulas come from, and how we check them: how we calculate.
How the weight loss calculator works
It takes the weight you want to lose, turns it into energy at about 7,700 kcal per kilogram, and spreads that over the days you give it. That daily gap is subtracted from your maintenance calories (TDEE, from the Mifflin-St Jeor equation and your activity level). The calorie deficit calculator goes the other way, from a chosen deficit to a number of weeks.
The conversion is the old rule of thumb that a kilogram of body weight is worth about 7,700 kcal (about 3,500 kcal per pound), which goes back to Wishnofsky (1958). It is an average. Hall and colleagues (The Lancet, 2011) showed that real weight change settles lower than that rule predicts, because a lighter body burns less, so read any timeline here as the earliest sensible estimate and re-run it at your new weight.
What it will not do
- It never goes below 1,200 kcal for women and 1,500 kcal for men. If your goal and dates would need less, the calculator shows the lowest target it will give and how many weeks the goal takes at that pace.
- It stops at a 1,000 kcal daily deficit. That is already a fast pace of roughly 0.9 kg a week; the CDC describes about 1 to 2 pounds a week as steady weight loss.
- It flags goal weights under the healthy BMI range for your height, and asks you to talk to a doctor or dietitian first.
Choosing the weeks
Slower is easier to keep up. Add weeks until the daily target feels like something you could eat on an ordinary Tuesday, not only on a good week. If you change your plan, run the calculator again from your new weight.