Precise fitness calculators, built like a good tool.
TDEE, macros, one-rep max, BMI and body fat. Each one uses a published equation from sources like the NHS, WHO and ACSM, and shows its working. Free and instant.
All calculators
Five tools, each with the math, the sources and a short FAQ.
TDEE Calculator
Daily calories you burn, from BMR and activity.
OpenMacro Calculator
Protein, carbs and fat grams for your calorie target.
OpenOne-Rep Max Calculator
Estimate your 1RM from a set, with a % loading table.
OpenBMI Calculator
Body Mass Index with WHO category thresholds.
OpenBody Fat Calculator
U.S. Navy circumference method, no calipers.
OpenFrequently asked questions
CalcFitLab is a set of free fitness calculators for the numbers behind training and nutrition — daily calories (TDEE), macros, one-rep max, BMI and body fat. Each tool uses a published equation rather than a guess, shows its working, and needs no sign-up. Below are the questions people ask most before they start.
Are the CalcFitLab calculators free to use?
Yes. Every calculator is free, with no sign-up, no email and nothing to install. You open a tool, enter your numbers and get a result in the browser. Nothing you type is stored on our side; the site is funded by a single link to the coaching platform that built it.
How accurate are the results?
Each tool uses a published equation rather than a made-up formula. TDEE uses Mifflin–St Jeor with standard activity multipliers, body fat uses the U.S. Navy circumference method, and one-rep max uses the Epley and Brzycki equations. For most people these land within a few percent — close enough to build training and nutrition around.
What is TDEE and why does it matter?
TDEE is your Total Daily Energy Expenditure — the calories you burn in a day, exercise included. It is the anchor for any nutrition plan: eat below it to lose fat, above it to gain, around it to maintain. The TDEE calculator estimates it from your height, weight, age, sex and activity level.
Which calculator should I start with?
Start with TDEE if your goal is fat loss or muscle gain, because every calorie and macro target is built on it. The macro calculator then splits those calories into protein, carbs and fat, and the one-rep max tool sets your training loads. BMI and body fat are useful checkpoints rather than starting points.
Do I need an account or a download?
No. There is no account, no download and no paywall. The calculators run entirely in your browser, so you can bookmark a tool and use it as often as you like without ever signing up.
Where do the formulas come from?
They are drawn from published sources — the NHS, WHO, ACSM and the original research papers behind each equation. The methodology page lists every formula and its source, so you can check the working instead of trusting a black box.
Can I use these calculators with coaching clients?
Yes. Coaches use them to set starting calorie and macro targets, estimate training loads and explain the numbers to clients. Treat the output as an estimate to build a plan around and adjust from real progress — it is not medical advice.