Free fitness calculators
Quick tools for training, diet and recovery. Each one shows its formula and its limits. They run in your browser, need no account, and send nothing anywhere.
- One rep max calculator
Estimate your 1RM from any set, with a percentage chart and RPE.
- Barbell plate calculator
See which plates go on each side of the bar for a target weight.
- TDEE calculator
Find your daily calories and macros to lose, keep or gain weight.
- Protein calculator
Get a daily protein range from your weight, goal and training.
- Sleep calculator
Bedtimes and wake times by sleep cycle, plus your weekly sleep debt.
- HRV calculator
Find your HRV baseline and normal range, and see how today compares.
These tools give general estimates, not medical advice.
Keep the numbers in one place
Marrow logs your lifts and food, sets calorie and macro targets, and reads sleep, HRV, resting heart rate, steps and weight from Apple Health. It is free, with an optional Pro.