FitCalculation

Free Fitness Calculators, With the Formula Shown

FitCalculation gives you free calculators for TDEE, calorie targets, macros, protein, BMI, and body composition. Every tool shows the equation it uses and the assumptions behind the result. There is no sign-up, no ads, and your numbers never leave your browser.

Browse calculatorsSee the formulas

  • Published formulas

    Every calculator names the equation it uses. No hidden multipliers.

  • Nothing leaves your device

    Calculations run in your browser. No account, no email, no tracking of your numbers.

  • Honest about error

    These are estimates. We show the assumptions instead of pretending to exactness.

Every calculator

16 tools, grouped by what you are trying to work out.

Energy Expenditure & Calories

How many calories should I eat each day?

Work out what you burn in a day, then turn that number into a daily calorie target for losing, maintaining, or gaining weight.

Start here

TDEE Calculator

Estimate the calories you burn each day from your basal metabolic rate and activity level.

BMR Calculator

Calculate your basal metabolic rate with Mifflin-St Jeor, and optionally Katch-McArdle if you know your body fat percentage.

Bulking Calculator

Work out the calories to eat while bulking and the daily protein target to aim for.

Macros & Protein

How do I split those calories?

Turn a calorie target into daily protein, carbohydrate, and fat targets, or set a protein intake on its own.

Start here

Macro Calculator

Split your daily calories into protein, fat, and carbohydrate targets.

Protein Calculator

Calculate your daily protein intake in grams and calories from your body weight and goal.

Body Composition

What is my body actually made of?

Measure body fat and lean mass, check BMI against the standard ranges, compare ideal body weight formulas, and plan a recomposition that keeps your lean mass.

Start here

Body Fat Calculator

Estimate your body fat percentage from simple tape measurements.

BMI Calculator

Check your body mass index and see where your weight falls on the standard range.

Ideal Body Weight Calculator

Compare the Devine, Robinson, Miller and Hamwi formulas side by side, with sources and limitations for each.

FFMI Calculator

Calculate your Fat-Free Mass Index and height-normalised FFMI from lean mass and height, with context on what the ranges mean.

Body Recomposition Calculator

Estimate your maintenance calories, a modest recomposition calorie target and a daily protein target for losing fat while keeping lean mass.

Fitness & Activity

How much am I burning through exercise?

Estimate calories burned from walking, find your one-rep max for strength training, and see how your lean mass compares with the FFMI.

Start here

Calories Burned Walking Calculator

Estimate calories burned from walking using MET values from the Compendium of Physical Activities, by speed, duration, or distance.

One Rep Max Calculator

Estimate your 1RM with Epley, Brzycki, Lombardi, Mayhew and O'Conner formulas, plus accuracy notes above 10 reps.

How it works

Three steps, no sign-up, and the same published method on every tool.

  1. Pick the number you need

    Start from TDEE if you want maintenance calories, or jump straight to a macro, protein, or body composition target.

  2. Enter your details

    Metric or imperial, no account required. Your inputs stay in the browser and are never sent anywhere.

  3. Read the result with its limits

    Each tool shows the formula and the assumptions behind the number, so you can judge whether it is useful for you.

How these numbers are calculated

Every calculator on this site is a published equation, not a black box. Here is the method behind each group of tools.

TDEE and BMR

Mifflin-St Jeor (1990), multiplied by an activity factor of 1.2 to 1.9

Resting burn is estimated from your age, sex, height, and weight, then scaled by how active a typical week is.

Calorie deficit and surplus

7,700 kcal per kilogram of body fat

A target rate of weekly change is converted into a daily calorie target, and a floor is applied so the result is never an unsafe intake.

Body fat percentage

U.S. Navy circumference method (Hodgdon-Beckett)

Estimated from height, neck, waist, and hip tape measurements. No scale required, and useful for tracking change over time.

Macronutrients

4 kcal per gram of protein and carbohydrate, 9 kcal per gram of fat

Protein and fat are set per kilogram of body weight, and carbohydrate takes the remaining calories.

Body composition

BMI, US Navy circumference, and lean mass from body fat

BMI divides weight by height squared. Body fat uses tape measurements. Lean mass subtracts fat percentage from weight.

Ideal body weight

Devine, Robinson, Miller, and Hamwi formulas

Four historical drug-dosing formulas shown side by side, none treated as authoritative.

Walking calories

MET × weight × time, from the Compendium of Physical Activities

Energy cost of walking estimated from speed-specific MET values and your body weight.

One-rep max

Epley, Brzycki, Lombardi, Mayhew, and O'Conner estimates

Five formulas estimate a theoretical maximum from a submaximal set. These are not safe-testing instructions.

FFMI

Lean mass / height², height-adjusted

Fat-Free Mass Index compares lean mass to height. The height correction aligns the scale across statures.

Terms these calculators use

The vocabulary behind the numbers, defined without the hand-waving.

TDEE — Total Daily Energy Expenditure
The total number of calories your body uses in an average day: your resting burn plus the energy spent moving, exercising, and digesting food. Eating around your TDEE is what holds your weight steady.
BMR — Basal Metabolic Rate
The calories your body burns at complete rest, measured while awake but totally inactive. TDEE is built on top of BMR by multiplying it by an activity factor.
Activity multiplier
The factor applied to your BMR to estimate TDEE, from 1.2 for sedentary up to 1.9 for very hard training or a physically demanding job. It describes your average week, not your hardest day.
Macros — Macronutrients
Protein, carbohydrate, and fat — the three nutrients that supply nearly all dietary energy. A macro split divides a calorie target into grams of each: 4 kcal per gram of protein and carbohydrate, 9 kcal per gram of fat.
BMI — Body Mass Index
A screening ratio of weight to height, calculated as weight in kilograms divided by height in meters squared, and placed against standard adult categories. BMI is a population screening measure, not a diagnosis: it cannot tell muscle from fat, so a muscular person can score high while carrying very little body fat.
Protein
The macronutrient that supports muscle repair and maintenance, worth 4 kcal per gram. This site sets a daily target from your body weight in kilograms — a range that rises on cutting and bulking goals, and falls back to a general range for maintenance.

Guides

A calculator gives you a number. These cover what to do with it.

All guides

Why these calculators are honest about being estimates

No formula can predict your exact calorie needs, and any tool that claims to is overselling. The Mifflin-St Jeor equation is reported to land within ±10% of measured resting metabolic rate for most adults, which means a real share of people fall outside that band in both directions.

On a 2,500 kcal day, a 15% error is 375 kcal. That is the difference between a real change and no change at all, which is why this site shows the equation, states the assumptions, and tells you how far to trust the answer rather than presenting a clean number as fact.

Where a figure is a rough screening measure rather than a measurement, it says so. BMI cannot tell muscle from fat, and a tape-measure body fat estimate is not a DEXA scan.

Use the result as a starting point, then adjust it against what actually happens to your weight over two to four weeks. That feedback loop is what makes an estimate accurate in practice, and no formula can replace it.

See every formula and its sourcesRead how these tools were built