Cutting Calorie Calculator

On this page

1. How the calculator sets your calories
2. Choose your speed
3. Protein on a cut
4. Keep training hard
5. How long to cut
6. Track the cut properly
7. When the scale stops moving
8. When to stop
9. Questions

How the calculator sets your calories

It estimates your maintenance calories (TDEE) first. That uses Mifflin-St Jeor by default, or Katch-McArdle if you enter your body fat, because lean-mass formulas tend to fit lean, muscular people better. Then it takes 10, 20 or 25% off.

Why a percentage and not the classic “500 calories a day”? Because 500 kcal means very different things to different people. For a woman who maintains on 1,800 kcal it is a 28% cut. For a large man who maintains on 3,200 kcal it is about 16%. A percentage scales with your size, so the effort feels similar for everyone.

The calculator then estimates your weekly loss with the rough rule of 7,700 kcal per kilo (3,500 per pound), shows that loss as a share of your body weight, sets protein from your weight and splits the rest of your calories into carbs and fat. It starts on the high-protein split; you can switch to balanced, low-carb or keto in the results.

Choose your speed

Research on trained people points the same way. In a study of 24 elite athletes, those who lost about 0.7% of their body weight a week gained lean mass and strength over the diet, while those losing about 1.4% a week only held on to the lean mass they had. Evidence-based guidelines for natural bodybuilders recommend about 0.5 to 1% of body weight a week for the same reason: slower loss gives your training a better chance of keeping up.

Speed also has a hunger cost. A bigger deficit feels harder every day, and most diets fail on adherence, not on maths. If you have tried fast cuts before and rebounded, start with steady and let consistency do the work.

The calculator warns you if a target falls below about 1,200 kcal (women) or 1,500 kcal (men) a day, a common floor without medical supervision, or if you would lose more than 1% of your weight a week.

Protein on a cut

Protein does two jobs in a deficit. It gives your muscles what they need to repair and hold on after training, and it keeps you fuller than the same calories of carbs or fat.

A 2018 meta-analysis of 49 trials found that the extra muscle from eating more protein while lifting levelled off at about 1.6 g per kg of body weight a day, with some people still benefiting up to about 2.2 g. In a deficit, needs probably sit at the higher end. In one four-week trial, young men eating 40% below their needs while training hard six days a week gained about 1.2 kg of lean mass on 2.4 g/kg of protein. The group on 1.2 g/kg gained almost none, and also lost less fat.

In practice:

• Aim for 1.6 to 2.2 g per kg of body weight a day. If you have a lot of fat to lose, the calculator bases this on a healthier weight for your height so the target doesn’t come out unrealistically high.
• Spread it over three to five meals of roughly 0.4 to 0.55 g per kg each, which is about 30 to 45 g for an 80 kg (176 lb) person.
• About 30 g of protein looks like 100 g of cooked chicken breast, a drained 145 g tin of tuna, 300 g of plain Greek yoghurt, 150 g of paneer or a scoop of whey in milk.

The protein calculator gives your exact range and a per-meal split.

Keep training hard

Lifting is the signal that tells your body your muscle is still needed. Keep your main heavy lifts in the plan and try to hold your strength. If recovery suffers late in a cut, trim a few sets rather than switching to light “toning” weights, which removes the signal you are trying to send.

Cardio is a tool, not a requirement. Walking burns extra calories with very little fatigue. Hard cardio on top of heavy leg training can eat into recovery, so add it gradually if you add it at all.

Watch your steps, too. When people eat less they often move less without noticing: fewer trips up the stairs, more sitting. Losing 3,000 steps a day can quietly cancel around 80 to 120 kcal of your deficit. A step target keeps that leak closed.

How long to cut

Plan in blocks rather than open-ended dieting. These are coaching rules of thumb, not lab-tested limits:

Breaks can help. In the 2018 MATADOR trial, men with obesity did 16 weeks of dieting either in one go or in two-week blocks separated by two weeks at maintenance. The group with breaks lost more weight and more fat, and kept more of it off six months later. You don’t have to diet that way, but a week or two at maintenance every 8 to 12 weeks is a sensible pressure valve for hunger, training and mood.

Track the cut properly

• Weigh most mornings under the same conditions and compare weekly averages, never single days.
• Expect a fast first week. Less food and fewer carbs mean less water and gut content. The real pace shows from week two or three.
• Measure your waist every two weeks at the navel. If your weight stalls but your waist keeps shrinking, you are still losing fat.
• Log your main lifts. Stable strength late in a cut is a good sign you are keeping muscle.
• Recalculate after every 4 to 5 kg (10 lb), because a lighter body needs less food.

When the scale stops moving

One flat week is noise. Two to three weeks with no change in your weekly average means something has shifted: you weigh less now, you may be moving less, or portions have crept up. Work through it in this order:

1. Log every bite for a week, weighing food where you can. Oils, drinks and weekend meals are the usual leaks.
2. Check your daily steps against the start of the cut.
3. If both look right, take 100 to 150 kcal a day off or add about 2,000 steps, then give it two more weeks.

Our weight loss plateau guide goes through every cause in more detail.

When to stop

End the cut and move to maintenance if you reach your goal, or if any of these show up:

• Your strength drops for two to three weeks in a row.
• Sleep, mood, focus or hunger become hard to manage.
• Your period becomes irregular or stops.
• You feel dizzy, cold all the time or unwell.

A missed or stopped period while dieting is a sign of low energy availability, which sports doctors call relative energy deficiency in sport (REDs). It affects bones, hormones and performance, so see a doctor rather than pushing on. The calculators on this site are for healthy adults; if you have a medical condition or a history of disordered eating, plan any cut with a professional.