Free macro calculator

How this macro calculator works

Every macro calculator is doing the same three things in sequence, and most of them never tell you which numbers they picked. This one shows its working, because the difference between two calculators giving you 1,900 and 2,400 calories is almost always a single assumption buried in step two.

Step one: your basal metabolic rate

Your basal metabolic rate, or BMR, is what your body burns doing nothing at all. Keeping your heart beating, your lungs moving and your brain running accounts for somewhere between 60 and 70 percent of everything you burn in a day, which is why it is the foundation of the whole calculation.

This calculator uses the Mifflin-St Jeor equation, published in 1990 and still the most accurate of the widely used predictive formulas. It reads:

• Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
• Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

You will still see the older Harris-Benedict equation on plenty of sites. It was developed in 1919 and revised in 1984, and it tends to overestimate by roughly 5 percent in modern populations. If a calculator hands you a suspiciously generous number, this is often why.

Step two: your activity multiplier

BMR is then multiplied by an activity factor to give your total daily energy expenditure, or TDEE: what you actually burn on a normal day. The standard factors run from 1.2 for someone sedentary up to 1.9 for someone doing physical work or training twice a day.

This is the step where calculators disagree, and it is where you are most likely to get it wrong yourself. The gap between lightly active at 1.375 and very active at 1.725 is worth several hundred calories a day for most people. Almost everyone overestimates here. Four gym sessions a week does not make you very active if you spend the other hundred waking hours sitting down. Pick the lower option when you are torn.

Step three: your goal adjustment

To lose fat, you eat below maintenance. A kilogram of body fat holds roughly 7,700 calories, so a target of half a kilogram a week works out at a deficit of about 550 calories a day. That is where the three pace options come from: steady, balanced and aggressive map onto 0.5, 0.7 and 1.0 kilograms a week.

Gaining is not the same arithmetic in reverse. Your body can only build muscle so quickly, and a surplus larger than that ceiling becomes fat rather than progress. So the gaining targets use conservative surpluses of 250 to 500 calories a day instead of mirroring the deficit maths.

The calculator also refuses to go below 1,200 calories for women or 1,500 for men, regardless of what the arithmetic produces. Those floors exist because a small, sedentary person on an aggressive deficit can mathematically land somewhere no one should eat without medical supervision.

Step four: splitting calories into macros

Protein comes first, set per kilogram of body weight and scaled by your goal and pace. Cutting demands the most, because protein is what stops your body breaking down muscle alongside fat when energy is scarce. Fat comes second, also per kilogram, with a floor that keeps hormone production intact. Carbohydrate then fills whatever calories are left, which is why it moves the most between goals.

Protein and carbohydrate provide 4 calories per gram, fat provides 9. That is the only conversion you need if you ever want to check the numbers by hand.

What to do with the result

Treat it as a hypothesis, not a prescription. Eat to these numbers for two to three weeks, weigh yourself under the same conditions a few times a week, and look at the trend rather than any single morning. If nothing is moving after three weeks, adjust calories by 10 percent and give it another three. Your real maintenance is whatever the scale says it is, not whatever an equation predicted.

One more thing worth saying plainly, since most calculators will not: the number is the easy part. Almost nobody fails because they calculated their macros wrong. They fail because logging every meal by hand is tedious enough that they stop doing it by week three. That is the problem worth solving, and it is the one Pocket Fit was built for.

Frequently asked questions

What is a macro calculator?

A macro calculator works out how many calories you should eat each day, then splits those calories into the three macronutrients your body runs on: protein, carbohydrate and fat. It uses your weight, height, age, sex and activity level to estimate what you burn, then adjusts that number up or down depending on whether you want to lose fat, gain muscle or get stronger.

How accurate are macro calculators?

Predictive equations like Mifflin-St Jeor land within about 10 percent of measured metabolic rate for most people, which is close enough to start with and not close enough to treat as gospel. Two people with identical stats can differ by several hundred calories a day. Use the result as a starting point, track it consistently for two to three weeks, and adjust based on what your weight actually does.

How much protein do I need to lose weight?

In a calorie deficit, protein does two jobs: it keeps you full, and it protects the muscle you already have from being burned alongside the fat. The research consistently supports somewhere between 1.6 and 2.4 grams per kilogram of body weight for people training in a deficit, and this calculator sits inside that range. The faster your chosen pace, the higher it goes.

Should I eat the same macros every day?

Consistency beats precision. Hitting roughly the same numbers most days will get you far better results than nailing them exactly on Monday and abandoning the whole thing by Thursday. Aim to land within about 10 grams of your protein target and let carbs and fat move around your day.

Do I need to weigh my food to hit my macros?

Weighing food is the most accurate way to track, and it is also the reason most people stop tracking within a fortnight. Photo-based logging trades a little accuracy for a lot of consistency, which is usually the better deal. Pocket Fit logs a meal from a single photo of your plate.

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