Free strength tools
Gym calculators for your next set.
No signup required. Estimate maxes, load the bar, plan nutrition, compare standards, and convert the result into something you can train from.
Core tool
1RM Calculator
Estimate your one-rep max from any submaximal set using 5 validated formulas with training percentages.
Core tool
TDEE Calculator
Calculate your total daily energy expenditure using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas.
Core tool
Macro Calculator
Get your ideal protein, carb, and fat targets for fat loss, maintenance, or muscle gain.
Training
BMR Calculator
Find your Basal Metabolic Rate — how many calories your body burns at complete rest using 3 validated formulas.
Training
Calorie Deficit / Surplus
Calculate your daily calorie target for fat loss or muscle gain with projected timeline to your goal weight.
Training
Strength Standards
Get a composite 0-999 strength score from your bench, squat, deadlift, OHP, and row relative to bodyweight.
Training
Plate Calculator
See exactly which plates to load on each side of the barbell with a color-coded visual breakdown.
Training
Body Fat Calculator
Estimate your body fat percentage using the US Navy method with body composition breakdown and category classification.
Nutrition
BMI Calculator
Calculate your Body Mass Index with an animated gauge, healthy weight range, BMI Prime, and Ponderal Index.
Nutrition
Protein Calculator
Find your optimal daily protein target with per-meal breakdown based on bodyweight, activity level, and training goal.
Nutrition
FFMI Calculator
Calculate your Fat-Free Mass Index with natural limit classification based on Kouri et al. (1995) research.
Nutrition
Wilks / DOTS / IPF GL
Calculate all three powerlifting bodyweight-normalized scores simultaneously from your total or individual lifts.
Nutrition
Exercise Alternatives
Find substitutes for any exercise from 873 movements, filtered by equipment type and grouped by category.
Nutrition
Progressive Overload
Get your next session prescription — add reps, increase weight, or deload — using RepStack's double progression engine.
How RepStack decides your next lift
Read the double-progression rule behind the calculator: add reps, bump weight, preserve e1RM, deload when the pattern says to.
Track less clutter
The workout log only matters if it changes the next session. Here is the cleaner tracking system.
RepStack for iPhone
Download RepStack
RepStack calculates your e1RM, TDEE, and macros automatically with every set you log.