Bulking calorie calculator

Estimate your calories

This uses the Mifflin-St Jeor equation, the one most dietitians reach for, and then multiplies it by how active your week is. Be honest about the activity level: it is where most people overestimate. What comes out is a starting estimate to test, not a personal requirement.

How to check the number is right for you

Every calculator is working from averages, so treat the figure as a first guess. Your own weight trend over two to three weeks tells you what no equation can (NHS, 2023).

1. Step 1

   Eat the number for two to three weeks

   Keep it roughly consistent day to day rather than swinging between extremes.

2. Step 2

   Weigh in the same way

   First thing in the morning, a few times a week, and look at the average rather than any single reading.

3. Step 3

   Read the trend, not the theory

   A slow, steady rise in the weekly average is the signal you are looking for. A controlled rate of gain has been associated with a better balance of lean mass to fat gain in a trial of elite athletes (Garthe et al., 2013); it is not an established optimal rate for beginners.

4. Step 4

   Adjust by about 150 calories

   Nothing moving after two to three weeks, add 150. Climbing faster than you want, take 150 off. Then give it another two to three weeks before judging again.

The size of the surplus you settle on is a judgement, not a solved number. For the reasoning behind how big it should be, read the guide to the calorie surplus for muscle gain; for your protein target in grams, use the protein calculator.

Filling the surplus with food that helps

A surplus made of protein and decent carbohydrates supports training. A surplus made of whatever fits mostly turns up as fat. The split matters less than people think, but protein does not.

Where the numbers usually go wrong

• Picking an activity level higher than your week really is
• Adding a 700 calorie surplus because faster sounds better
• Changing the number every few days based on one weigh-in
• Forgetting drinks, oils and what you eat at the weekend
• Eating the target on training days only

Why your maintenance number keeps changing

Maintenance is not a fixed property of your body. It is the sum of four things, and three of them move week to week, which is why a figure that worked in January can be 200 calories out by March.

The largest single component scales with how much you weigh, so as you gain, maintenance rises with you and the surplus you started with quietly shrinks. That is the usual reason weight gain stalls after a good first month, rather than anything having gone wrong.

How much of the gain will be muscle

Nobody gains only muscle. Some fat comes with it, and the size of the surplus is the main thing deciding the ratio. A modest surplus in a trained beginner tends to split reasonably well; a large one mostly buys fat, because muscle can only be built at the speed your body can build it, however much you eat.

These are practical patterns rather than fixed rules, and no row here is an established optimum. A given number of calories does not translate into a set weekly weight gain either: the same surplus is small for a large, active adult and substantial for a smaller, less active one. The scales alone also cannot tell you which tissue you gained, because water shifts with salt, carbohydrates and training. Waist measurements alongside weight give you a far better read: weight up and waist steady is the pattern you want.