Calorie Calculator for Bulking and Cutting

How the calculator works out your calories

First the calculator works out your resting metabolic rate with the Mifflin-St Jeor equation: for men 10 × weight in kg + 6.25 × height in cm − 5 × age in years + 5, for women the same but − 161 at the end instead of + 5.

It multiplies the result by a rough activity factor: 1.5 for 3-4 workouts a week and a desk job, 1.7 for lots of movement during the day, 1.3 if you don't move much. That's your maintenance: the calories at which your weight stays the same.

To start a bulk the calculator adds about 5% to maintenance; to start a cut it takes off 10%, or 15% with high body fat. Example: a man, 90 kg, 182 cm, 32 years old, 4 workouts a week and a desk job. His resting rate is about 1,880 kcal, his maintenance about 2,820 kcal and his starting cut calories about 2,540 kcal.

Mifflin-St Jeor predicts resting metabolic rate within 10% more often than three other popular equations, but for a single person it can be further off. That's why you start with a small deficit or a small surplus and correct your calories in steps. You shouldn't cut before 18, so the calculator accepts ages 18 and up.

The pace of a cut depends on your body fat

The less body fat you start with, the more of the weight you lose comes from lean mass, and a bigger deficit pushes that share higher. That's why a lean person loses weight more slowly and has a lower deficit cap than someone with high body fat.

The thresholds in the table are our practice. The pace of 0.5-1% of body weight a week comes from recommendations for natural bodybuilders, and the 30% cap from obesity treatment guidelines. The calorie floor is your resting rate from the formula, and never less than 1,500 kcal for men and 1,200 kcal for women.

The pace of a bulk: 0.25-0.5% of body weight a week

On a bulk your weight should go up 0.25-0.5% a week: 0.2-0.4 kg at 80 kg, 0.25-0.5 kg at 100 kg. The longer you've been training, the closer to the low end.

Gaining faster mostly adds fat: in a study of trained lifters, squat strength and muscle thickness grew about the same with a 0%, 5% and 15% surplus, the bench press a little better at 15%, and the bigger surplus mostly added skinfold thickness. That's why the surplus starts at about 5% and goes up in steps of 150-200 kcal; if your weight stalls, the steps reach 10-15%.

Correcting calories every 2 weeks

For 2 weeks, eat the same amount every day, weekends included. Weigh yourself in the morning, after the bathroom and before eating, ideally every day, and compare weekly averages, because a single weigh-in bounces around with water, salt and food.

Ignore the first week: that's when you lose water and glycogen on a cut and gain them on a bulk. After that, change your calories by 150-200 kcal a day and wait another 2 weeks. On a cut 2-3 steps are usually enough, so you reach your target deficit in week 6-8.

After 4 weeks of steady eating, your weight tells you more than the formula. On a cut your maintenance is your average daily calories plus your weekly weight loss in kg × 1,000: you eat 2,150 kcal and lose 0.45 kg a week, so your maintenance is about 2,600 kcal. On a bulk you subtract your weekly gain in kg × 700 from your average calories.

When not to cut

Don't cut under 18, during pregnancy, with a BMI under 18.5 or with an eating disorder. With a BMI under 18.5, the calculator shows only your maintenance instead of a deficit.

If your period stops during a cut, go back to eating at maintenance and see a doctor.

Frequently asked questions