Bulking Calorie Calculator
A bulk is a period where you eat above maintenance so your body has the surplus energy it needs to build new muscle. This calculator estimates your maintenance calories from your bodyweight, height, age, and activity, then adds a surplus of 10 to 20 percent, which works out to roughly 250 to 500 extra calories per day for most lifters. That is enough to fuel growth without piling on unnecessary fat.
The honest catch is that muscle is built slowly, so a bigger surplus does not speed it up past a point, it just adds fat. Expect to gain roughly 0.5 to 1 percent of your bodyweight per month on a standard bulk. Faster than that and most of the extra scale weight is fat you will have to diet off later, so patience with the surplus is what keeps a bulk productive.
How maintenance is estimated
Maintenance is your total daily energy expenditure (TDEE), the calories you burn in a day. The calculator first finds your basal metabolic rate (BMR) with the Mifflin-St Jeor equation: for men, BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5, and for women the same formula ends in - 161 instead of + 5. If you enter a body fat percentage, it switches to the Katch-McArdle equation, BMR = 370 + 21.6 x lean mass(kg), which uses lean mass and is more accurate when your body fat is known.
BMR is then multiplied by an activity factor to get maintenance: sedentary x 1.2, light x 1.375, moderate x 1.55, active x 1.725, and very active x 1.9. Pick the level that matches your typical week, since overstating your activity is the most common reason a calculated surplus turns into a bigger one than intended.
How the surplus works
The target adds 10 to 20 percent on top of maintenance, which is roughly 250 to 500 calories per day for most lifters. That range is large enough to support muscle protein synthesis and progressive overload in the gym, while staying small enough that you are not gaining fat faster than you are gaining muscle.
At this surplus you should gain about 0.5 to 1 percent of your bodyweight per month. Bigger surpluses do not build muscle any faster, because the rate of muscle growth is capped by your training and recovery, not by how much you eat. Every calorie beyond what growth can use is stored as fat, so a larger surplus mostly buys you a longer cut later.
Frequently asked questions
How many calories should I eat to bulk?
Eat about 10 to 20 percent above your maintenance calories, which is roughly 250 to 500 extra calories per day for most lifters. Start at the lower end of that range if you are prone to gaining fat easily, and adjust based on how fast the scale moves over two to three weeks.
How fast should I gain weight on a bulk?
Aim for roughly 0.5 to 1 percent of your bodyweight per month. For a 180 lb lifter that is about 1 to 2 lb per month. Gaining much faster than this means most of the extra weight is fat rather than muscle, because muscle can only be built so quickly.
Should I bulk or cut first?
It mostly comes down to your current body fat. If you are above roughly 15 to 20 percent body fat as a man (or 25 to 30 percent as a woman), cut first so you start your bulk lean and can gain for longer before getting soft. If you are already lean, start bulking.
Do I need to eat clean to bulk?
Food quality matters for satiety, digestion, and overall health, and whole foods make it easier to hit protein and micronutrients. But it is the size of your surplus, not the cleanliness of your food, that determines how much fat you gain. You can gain fat eating clean if you overshoot, and stay lean eating some processed food if your total calories are controlled.