Weight Loss Calculator

The daily calories to reach your goal weight and a projected finish date — from your TDEE and a loss rate you choose, with honest safety limits built in.

Sex
Age years
Height cm
ft in
Current weight kg lb
Goal weight kg lb
Activity level
  • Sedentary — little or no exercise
  • Light — exercise 1–3 days/week
  • Moderate — exercise 3–5 days/week
  • Active — exercise 6–7 days/week
  • Very active — hard exercise or physical job
Loss rate
  • Relaxed — 0.25 kg (0.55 lb) / week
  • Steady — 0.5 kg (1.1 lb) / week
  • Fast — 0.75 kg (1.65 lb) / week
  • Maximum — 1 kg (2.2 lb) / week
Eat about
—kcal/day Enter your details

Based on your TDEE minus the deficit for your chosen rate (~7,700 kcal per kg). Guidelines generally recommend 0.25–0.5 kg (0.5–1 lb) per week — slower loss preserves more muscle and is easier to keep off. Don't eat below 1,200 kcal (women) / 1,500 kcal (men) without medical supervision.

Losing weight is an energy-budget problem: eat consistently below what you burn and the difference comes out of stored fat. This calculator does the budgeting — your maintenance calories, the daily target for the loss rate you choose, and the date you’d reach your goal — with the safety rails that most calculators skip.

The math, in the open

  1. Maintenance (TDEE): Mifflin-St Jeor BMR from your sex, age, height, and weight, times an activity factor.
  2. The deficit: a kilogram of body fat stores roughly 7,700 kcal, so each 0.5 kg/week of planned loss needs about a 550 kcal daily deficit.
  3. The timeline: total weight to lose ÷ weekly rate = weeks; the calculator dates it on the calendar and shows all four standard rates side by side.

The safety rails

Two warnings are built in, because an honest tool should refuse to pretend everything is fine:

  • Aggressive pace — rates above ~1% of body weight per week accelerate muscle loss and rarely hold. Guidelines favor 0.25–0.5 kg (0.5–1 lb) weekly.
  • Below the floor — if your target drops under 1,200 kcal (women) / 1,500 kcal (men), the calculator says so. Below those intakes it’s hard to cover protein and micronutrient needs without supervision; a slower rate or more daily movement is the better lever.

Why the scale won’t cooperate weekly

Kevin Hall’s modeling work (see references) showed the old “3,500 calories = a pound, forever” rule overstates long-term loss: as you shrink, your maintenance shrinks too, so a fixed intake produces slowing loss — not a straight line. Practical upshot: weigh daily, judge by the weekly average, expect a fast watery first week, and recalculate your target every few kilograms. Consistency over months, not perfection over days, is the entire game.

Frequently asked questions

How does the weight loss calculator work?

It estimates your maintenance calories (Mifflin-St Jeor BMR × activity), then subtracts the daily deficit for your chosen rate — about 1,100 kcal/day per kilogram per week, from the ~7,700 kcal stored in a kilogram of body fat. The result is a daily calorie target and a projected date you reach your goal.

How fast should I lose weight?

Mainstream guidance is 0.25–0.5 kg (0.5–1 lb) per week, or up to about 1% of body weight weekly. Faster than that loses more muscle and water, is harder to sustain, and rebounds more often. The calculator flags rates above 1% of your body weight as aggressive.

Why shouldn't I just eat as little as possible?

Below roughly 1,200 kcal/day for women or 1,500 for men it becomes very difficult to get adequate protein and micronutrients, and adherence collapses. The calculator warns when a chosen rate pushes your target under those floors — pick a slower rate or add activity instead.

Will the projected date be exact?

No — treat it as a trajectory, not a promise. Early loss includes water weight, metabolism adapts slightly as you get lighter, and life happens. Recalculate every few weeks at your new weight; the finish date will firm up as you go.

References