Every tool here pulls its multipliers from primary sources. The numbers you get are the same numbers you would get from reading a meta-analysis, only faster. Use them as a starting point, not as a substitute for working with a clinician when one is appropriate.
Protein Calculator
How much protein per day for muscle gain, fat loss, endurance, or general health. Built on the 2018 BJSM meta-analysis of 49 RCTs (Morton et al.) and the ISSN position stand on protein and exercise.
Open calculator → CalculatorBMI & Waist-to-Height Ratio
WHO BMI categories paired with the Ashwell 2012 waist-to-height ratio, which outperforms BMI for cardiometabolic risk. Catches the muscular-but-flagged-overweight false positive and the normal-BMI-with-hidden-visceral-fat case.
Open calculator → CalculatorTDEE & Calorie Calculator
Daily calorie needs via Mifflin-St Jeor (validated by Frankenfield et al. 2005), with an optional Katch-McArdle path when body fat percent is known. Returns BMR, TDEE, and goal-aware cut, maintain, and bulk targets.
Open calculator → CalculatorMacro Calculator
Goal-aware protein, fat, and carbohydrate targets for cutting, maintenance, or bulking. Protein per Morton 2018, fat floor per ISSN, calibrated for training experience and age. Includes per-meal breakdown.
Open calculator → CalculatorBody Fat Calculator
US Navy circumference method (Hodgdon & Beckett 1984, r=0.90 vs hydrostatic weighing) with explicit accuracy bands. Optional 3-site Jackson-Pollock skinfold mode for caliper users.
Open calculator → Calculator1 Rep Max Calculator
Strength estimator averaging Epley, Brzycki, and Lombardi formulas. Shows the spread, applies Reynolds 2006 accuracy bands, and includes a percentage table for hypertrophy, strength, and power.
Open calculator →Body Recomposition Planner
Combine your protein target with a small calorie deficit and a sensible training stimulus to gain muscle and lose fat at the same time.
In developmentWhy these tools exist
Most fitness calculators online are built to capture an email address or sell a supplement. The numbers they produce are often cribbed from secondary sources, padded for safety, or tuned to push you toward a product. We took the opposite approach.
Each tool here cites the studies it relies on. The defaults match peer-reviewed consensus where consensus exists, and ranges where it doesn't. The tools run entirely in your browser. We don't store your inputs, don't track your results, and don't gate the output behind a signup form.
Who builds these
The tools are designed by Domenic Angelino, FitCraft's Chief Exercise Scientist. He holds an MS in Kinesiology and an MPH from Brown University, is NSCA-certified as a Strength and Conditioning Specialist, and has been published in the Journal of Strength and Conditioning Research, Medicine & Science in Sports & Exercise, and Frontiers in Physiology.