How your calorie and protein
targets are calculated.

Step 1. Your resting metabolism

The starting point is resting energy expenditure, the energy your body uses at complete rest. Phasebuilt estimates it with the Mifflin St Jeor equation, published in 1990 and still one of the most widely used predictive equations in clinical practice.

(10 × weight in kg) + (6.25 × height in cm) − (5 × age in years)
then +5 if you selected male, or −161 if you selected female

Source: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 1990;51(2):241 to 247.

Step 2. Your daily energy needs

Resting metabolism only describes you at rest. To estimate what you actually burn in a day, the builder multiplies it by the activity factor matching the option you chose:

Mostly seated

× 1.2

Lightly active

× 1.375

Moderately active

× 1.55

Very active

× 1.725

The result is your maintenance level: roughly the intake at which your weight holds steady.

Step 3. The adjustment for your goal and pace

Your goal sets the direction and your chosen pace sets the size of the change. Pace exists because the fastest option is rarely the one people finish.

Fat loss, gentle

250 calories below maintenance

Fat loss, steady

375 calories below maintenance

Fat loss, ambitious

500 calories below maintenance

Muscle gain, gentle

150 calories above maintenance

Muscle gain, steady

225 calories above maintenance

Muscle gain, ambitious

325 calories above maintenance

If your goal is general fitness, no adjustment is applied and you train at maintenance.

Step 4. The recovery safeguard

If you report sleeping under six hours, or high stress, a fat loss deficit is reduced by 100 calories. Recovery is where training adaptation actually happens, and a large deficit stacked on poor sleep tends to cost you training quality and lean mass rather than speed the result up. The safeguard is applied automatically, so an honest answer about your sleep produces a more usable plan than an optimistic one.

Step 5. Protein, fat and carbohydrate

Protein

1.8 g per kg of bodyweight, raised to 2.0 g per kg when your goal is building muscle

Fat

0.8 g per kg of bodyweight

Carbohydrate

Fills whatever calories remain, with a floor so the target never drops unreasonably low

Protein is set first because it is the macronutrient most worth protecting in a deficit. Fat is held at a level that supports normal hormonal function. Carbohydrate takes the remainder, which is why it moves the most between goals.

A worked example

These are the actual figures the builder produces for a 34 year old man, 178 cm, 82 kg, moderately active, fat loss at a steady pace, sleeping 7 to 9 hours:

Resting metabolism

(10 × 82) + (6.25 × 178) − (5 × 34) + 5 = 1,768 calories

Maintenance

1,768 × 1.55 = 2,740 calories

Steady fat loss target

2,740 − 375 = 2,365 calories

Protein

82 × 1.8 = 148 g

Fat

82 × 0.8 = 66 g

Carbohydrate

the remaining calories, 295 g

Had the same person reported under six hours of sleep, the safeguard would lift the target to 2,465 calories.

So how many calories should I eat?

There is no single number that applies to everyone, which is why the question is usually answered badly. It depends on your size, age, sex, how much you move and what you are trying to do. The five steps above turn those into one figure for you specifically, and the worked example shows the whole chain from 1,768 calories at rest to a 2,365 calorie daily target.

If you want the number without doing the arithmetic, the builder produces it in about a minute.

And how much protein should I eat?

Phasebuilt uses 1.8 g per kilogram of bodyweight, rising to 2.0 g per kg when you are building muscle. That sits inside the 1.4 to 2.0 g per kg range the International Society of Sports Nutrition gives for active people building or maintaining muscle. For an 82 kg person that is roughly 148 g a day, or 164 g when building.

Does it give you a meal plan too?

Yes. Alongside the targets, the plan lays out meals for the diet you selected, whether that is balanced, high protein, vegetarian, vegan or low carb, with per meal calorie and protein guidance and food lists to build from. It works around allergies and foods you say you dislike. It is a free meal plan in the only sense that matters: no account, no payment, no upsell.

What this method does not do

Predictive equations estimate a population average, not you specifically. Individual resting metabolism varies around the prediction, so treat the output as a well reasoned starting point rather than a measured fact. The number that matters is what happens over the following two to three weeks: if weight and performance are not moving the way you expected, the target needs adjusting, and no equation can skip that step.

Phasebuilt also does not account for medical conditions, medication, pregnancy or postpartum recovery. It provides general fitness information for healthy adults, not medical advice.

Related: what a 90-day workout plan actually contains.