Weight Loss Calculator

It first estimates your TDEE from current weight, height, age, sex, and activity level using the Mifflin-St Jeor equation, then subtracts a deficit sized to your chosen weekly rate — 550 kcal/day for 0.5 kg/week, 825 for 0.75 kg/week, or 1,100 for 1.0 kg/week. Those figures come from the roughly 7,700 kcal held in a kilogram of body fat, spread across 7 days, not the rounder but less accurate 1,000 kcal/kg/week some sources use.

A full kilogram a week means a sustained 1,100 kcal/day deficit, which is the range general guidance treats as requiring medical oversight rather than something to do unmonitored. The moderate 0.5 kg/week setting is the rate most guidelines describe as sustainable without supervision for most adults.

Treat it as an order-of-magnitude estimate, not a delivery date. The timeline is a straight-line calculation — total kilograms to lose divided by your chosen weekly rate — but real weight loss isn't linear: the first week or two often includes a larger drop that's water weight rather than fat, and the rate itself slows over time as your TDEE falls with your body weight.

Because TDEE is calculated once, from your starting weight, and doesn't update automatically as you lose weight. A target that produces 0.5 kg/week at 80 kg will produce a slower rate by the time you reach 74 kg unless you recalculate — generally worth doing every 5-8 kg lost, or every few weeks.

No. It's built for adults with overweight or obesity planning a gradual, sustained loss, and explicitly doesn't apply to pregnant or breastfeeding people, anyone already at a healthy weight, or anyone with a history of disordered eating, for whom calorie tracking and timelines can be harmful regardless of what the numbers say.