How big is a calorie deficit?

A moderate deficit for weight loss is 15–20% of your maintenance (TDEE), usually 300–600 kcal a day. That gives about −0.25…−0.5 kg per week without losing muscle. The calculator works out the exact figure for your pace.

How big should the deficit be to lose weight?

A guide: a deficit of ~550 kcal a day ≈ −0.5 kg per week (1 kg of fat ≈ 7700 kcal). A gentle pace needs ~275 kcal, a fast one up to ~1100 — but never below the safe calorie floor.

How many calories to eat per day to lose weight?

Your TDEE minus the deficit for the chosen pace. The calculator works this out from sex, age, height, weight and activity and never drops calories below the safe floor (BMR and ~1200/1500 kcal).

How do you create a calorie deficit?

Two levers: eat less (lower the calories in your diet) and move more (raise expenditure). The most sustainable path is to trim food moderately and add activity/steps rather than starve. A steep deficit slows metabolism and ends in rebound.

Can you lose weight in a deficit without exercise?

Yes — weight drops from the calorie deficit itself, and exercise is not required for it. But strength training and protein help keep muscle instead of losing it with the fat, and protect your metabolism. Without exercise, diet just matters more.

Why am I not losing weight in a deficit?

Usually underestimated calories, water retention or too steep a deficit. But if weight genuinely holds in a clear deficit for weeks, the cause may be insulin resistance, hypothyroidism, iron deficiency or high cortisol — which shows up in blood tests.

How accurate is the calculator?

It is an estimate with a ±10% spread: the formulas give an average expenditure, while your real one depends on body composition, hormones and adaptation. Use the figure as a start and adjust by your weight trend over 2–3 weeks.

Calorie deficit calculator for weight loss

A calorie deficit is when you burn more energy over the day than you take in from food, and your body makes up the difference from fat stores. This calculator works out your maintenance level (TDEE), then for the pace you choose it shows how many calories to eat per day, how big the deficit is, how fast you lose weight and how many weeks to reach your goal. Enter your body fat and the estimate gets sharper (Katch-McArdle), with protein based on lean mass.

Calculate your calorie deficit for weight loss

Fill in sex, age, height and weight — your plan appears instantly.

What a calorie deficit is and how it works

Weight drops when there is an energy deficit: fewer calories from food than the body spends in a day. The body draws the shortfall from its stores — mostly fat, but with too steep a deficit and no protein or training, muscle too. So what matters is not the biggest deficit, but a sustainable one.

A guide: about 7700 kcal roughly equal 1 kg of fat tissue. It is a simplification (real expenditure shifts as you lose weight and metabolism adapts a little), but it works for planning: a deficit of ~550 kcal a day is about −0.5 kg per week.

How many calories to eat to lose weight

The starting point is your TDEE, the daily expenditure including activity. To lose weight you subtract a deficit from it. A moderate deficit is 15–20% of TDEE (usually 300–600 kcal) — this gives steady weight loss without crashes or rebound.

The calculator shows four paces: gentle (−0.25 kg/wk), moderate (−0.5), fast (−0.75) and aggressive (−1 kg/wk). The faster the pace, the bigger the deficit and the stricter the diet; for most people the moderate pace is optimal.

How to calculate a calorie deficit

First the basal metabolic rate (BMR) is computed with the Mifflin–St Jeor equation from sex, age, height and weight. BMR is multiplied by an activity factor to give TDEE, your maintenance level. The deficit for the chosen pace: the target rate in kg/wk is converted into daily calories (via 7700 kcal/kg) and subtracted from TDEE.

If you enter body fat, metabolism is computed with Katch-McArdle from lean mass — more accurate for lean and muscular people. The output is your daily calories, the deficit size and the macro split for it.

The safe calorie floor

Too large a deficit backfires: it slows metabolism, costs muscle, hits sleep, mood and hormones and almost always ends in rebound. So the calculator never drops calories below a safe floor — not below your BMR and not below roughly 1200 kcal for women and 1500 for men when losing weight without medical supervision.

If the chosen pace would need calories below that floor, the calculator raises intake to the minimum and honestly shows that the real rate of loss will be slower than selected. Faster is not better.

Why the scale stalls even in a deficit

Common reasons for “not losing in a deficit”: underestimated calories (snacks, oil, drinks, sauces by eye), water retention after salt, training or your cycle, too steep a deficit with metabolic slowdown, and real metabolic brakes — insulin resistance, hypothyroidism, iron deficiency, high cortisol.

If weight genuinely holds for 3–4 weeks in a clear deficit, it is often not about willpower but about what is slowing metabolism. That shows up in blood tests, not in a calculator.

FAQ

A moderate deficit for weight loss is 15–20% of your maintenance (TDEE), usually 300–600 kcal a day. That gives about −0.25…−0.5 kg per week without losing muscle. The calculator works out the exact figure for your pace.
A guide: a deficit of ~550 kcal a day ≈ −0.5 kg per week (1 kg of fat ≈ 7700 kcal). A gentle pace needs ~275 kcal, a fast one up to ~1100 — but never below the safe calorie floor.
Your TDEE minus the deficit for the chosen pace. The calculator works this out from sex, age, height, weight and activity and never drops calories below the safe floor (BMR and ~1200/1500 kcal).
Two levers: eat less (lower the calories in your diet) and move more (raise expenditure). The most sustainable path is to trim food moderately and add activity/steps rather than starve. A steep deficit slows metabolism and ends in rebound.
Yes — weight drops from the calorie deficit itself, and exercise is not required for it. But strength training and protein help keep muscle instead of losing it with the fat, and protect your metabolism. Without exercise, diet just matters more.
Usually underestimated calories, water retention or too steep a deficit. But if weight genuinely holds in a clear deficit for weeks, the cause may be insulin resistance, hypothyroidism, iron deficiency or high cortisol — which shows up in blood tests.
It is an estimate with a ±10% spread: the formulas give an average expenditure, while your real one depends on body composition, hormones and adaptation. Use the figure as a start and adjust by your weight trend over 2–3 weeks.

In a deficit but the scale won’t move? Your labs show why

A metabolic program from your blood work: AI finds what is braking your weight — insulin, thyroid, ferritin, cortisol — and builds a plan for you.

Find what’s braking weight

This calculator is for reference and information only and does not replace a doctor or dietitian. The result is an averaged estimate with a ±10% spread; it is not for children, pregnancy or metabolic conditions. Do not go below the safe calorie floor without professional supervision.