Calorie deficit calculator

How long a given daily deficit takes to reach your goal weight — and, just as usefully, whether the rate you've picked is one you can actually live with.

Milo

500 a day is the usual starting point. It’s the gap between what you eat and what you burn, not what you eat.

Your timeline will appear here.

How this is worked out

A kilo of body mass carries roughly 7,700 calories. So the arithmetic is simply the gap between where you are and where you want to be, times 7,700, divided by your daily deficit.

days = (weight to lose × 7700) ÷ daily deficit

The rate matters more than the total. Losing more than about 1% of your bodyweight a week increasingly takes muscle with the fat, and the appetite response gets harder to hold. Below that, most of what goes is fat.

Treat the answer as a direction, not a date. Water and glycogen swing the scale by a kilo or two within any given week, and your maintenance drops as you get lighter, so the same deficit buys less as you go — the last stretch always takes longer than the straight-line maths suggests.

The number is the easy part

Any calculator can hand you a figure. The hard bit is the next three months: eating roughly to it, noticing when it stops working, and changing it. Milo is a coach you text like a friend. You log what you ate in a sentence, and it learns your patterns, notices when your weight stalls, and adjusts the target from what you actually did rather than from a formula.

See how Milo works

Common questions

Is 7,700 calories per kilo exact?

It’s a planning figure, derived from the energy in body fat. Early weight loss is partly water, so the first week often looks faster than it should, and a whoosh after a stall is usually water rather than fat. Over months it averages out reasonably well.

What deficit should I pick?

500 a day is the usual starting point, giving roughly half a kilo a week. If you’re heavier you can hold a bigger one comfortably; if you’re already lean, a smaller one protects your training and your mood. The best deficit is the biggest one you won’t abandon.

Why has my weight stalled when I'm still in a deficit?

Usually one of three things: the deficit has shrunk because you’re lighter than when you calculated it, portions have crept up without being logged, or you’re holding water — which is common after a hard session or a salty meal. Stalls under two weeks are usually noise.

Can I use this to gain weight?

Yes. Put a goal weight above your current one and the same maths runs in reverse. For lean gain, aim slower than you would for loss: roughly 0.25 to 0.5% of bodyweight a week, or most of what you add is fat.

Other calculators

These are estimates from population averages, not measurements of you. Individual metabolism varies by roughly ±10% around any formula. Nothing here is medical advice — if you have a health condition, are pregnant, or are under 18, talk to a healthcare professional before changing how you eat or train.