Calorie Calculator - Daily Calorie Needs | Morph

Find out how many calories you actually need

This calorie calculator estimates how many calories your body burns in a day so you can set a target for losing weight, maintaining it, or gaining. You enter your age, sex, height, weight, and activity level, and it returns your maintenance calories along with adjusted targets for each goal.

The math behind it is the Mifflin-St Jeor equation, which is the formula most dietitians and registered nutritionists use today because it tracks real-world resting metabolic rate more accurately than the older Harris-Benedict formula. The calculator first finds your basal metabolic rate (BMR) - the energy your body uses at complete rest - then multiplies it by an activity factor to get your total daily energy expenditure (TDEE).

How the numbers work

BMR is what you'd burn lying in bed all day. It's driven mostly by your lean body mass, which is why height, weight, age, and sex all matter.
TDEE adds movement: a desk job with no exercise sits around 1.2x BMR, while training hard six days a week pushes past 1.7x.
Weight loss is usually a 300-500 calorie daily deficit, which lines up with the commonly cited rate of roughly half a pound to one pound per week. Aggressive deficits below your BMR are flagged because they're hard to sustain and can cost you muscle.
Weight gain adds a moderate surplus, the sensible approach if you're trying to build muscle without excess fat.

Why run it in your browser

Everything calculates on your own device. Your weight, age, and goals never leave your computer or phone - there's no account, no server call, and nothing stored. For numbers as personal as body stats, that matters. You can run it as many times as you want, compare goals side by side, and close the tab knowing nothing was saved anywhere.

A calorie target is a starting estimate, not a prescription. Real metabolism varies with genetics, sleep, stress, and how much muscle you carry, so treat the result as a baseline. Track how your weight actually responds over two or three weeks and adjust your intake up or down from there. If you have a medical condition, are pregnant, or are managing an eating disorder, talk to a doctor or registered dietitian before setting a calorie goal.

Pair this with the BMI calculator for a quick body-weight snapshot, or the BMR calculator if you only need your resting burn rate.

How to use

Enter your details — Type in your age, biological sex, height, and current weight using whichever units you prefer (metric or imperial).
Pick your activity level — Choose the option that matches a typical week, from sedentary (little exercise) up to very active (hard training most days). Be honest - overestimating here is the most common reason targets feel off.
Read your maintenance number — The calculator shows your TDEE - the calories that keep your weight stable. This is your anchor point.
Choose a goal — See the adjusted targets for losing, maintaining, or gaining weight, each with a sensible daily deficit or surplus already applied.
Track and adjust — Use the target for two to three weeks, watch how your weight responds, then nudge the number up or down based on real results.

Frequently asked questions

Which formula does this calorie calculator use?

It uses the Mifflin-St Jeor equation to calculate your basal metabolic rate, then applies an activity multiplier to estimate total daily energy expenditure. Mifflin-St Jeor is the standard most nutrition professionals rely on because it predicts resting metabolism more accurately than older equations for most people.

Is my personal data uploaded anywhere?

No. The calculator runs entirely in your browser on your own device. Your age, weight, height, and goals are never sent to a server, never stored, and there's no account to create. Close the tab and nothing remains.

How accurate is the calorie estimate?

It's a solid starting point, typically within about 10 percent of your real needs. Actual metabolism varies with muscle mass, genetics, sleep, and stress, so the best approach is to use the estimate for a few weeks and adjust based on how your weight actually changes.

How big a calorie deficit should I use to lose weight?

A daily deficit of 300 to 500 calories is the common, sustainable range and corresponds to roughly half a pound to one pound of weight loss per week. The calculator warns if a target dips below your BMR, since very aggressive deficits are hard to maintain and can cost lean muscle.

Do I need to count calories perfectly?

No. The goal is consistency, not perfection. Use the target as a guide, weigh yourself on the same day each week, and look at the trend over time rather than any single day. Adjust the number if your weight isn't moving the way you expect.