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Calorie Deficit Calculator

Pick a pace, see the daily gap it needs and how long it would take.

What this calculates

A kilogram of body fat holds roughly 7,700 calories, so a rate of loss and a daily gap are the same fact expressed two ways. The useful question is not how big a deficit you can tolerate for a fortnight, but which one you will still be running in three months.

Common questions

What is a safe deficit?

Most guidance sits at 0.5–1% of body weight a week, which for most people means a gap of 300–750 calories a day. Larger gaps work faster and cost more — more muscle lost, more hunger, and a much higher chance of stopping early.

Why has my loss stalled?

Usually one of three things: portions have quietly grown, your maintenance has fallen because you are lighter, or you are looking at water rather than fat. Recalculate at your current weight, tighten logging for a fortnight, and judge on weekly averages.

Is it better to eat less or move more?

Both, in a mix. Taking the whole gap out of food gets hard to sustain and costs more muscle; trying to take it all from exercise means a lot of training. Covering roughly a third with movement is a reasonable default.

Do I need a deficit every day?

No — the week is what counts. Some people do better with a couple of higher days and five lower ones, which leaves room for a dinner out without the plan collapsing.

Estimates for healthy adults — not medical advice, diagnosis or treatment. If you are pregnant or breastfeeding, under 18, managing a condition such as diabetes or thyroid disease, or have a history of disordered eating, talk to a doctor or a registered dietitian before acting on any of this.

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Content last reviewed 29 August 2026. Estimates for healthy adults, not medical advice.