Overview
What Is a One Rep Max Calculator?
This tool estimates your one-repetition maximum (the most weight you could lift for a single rep) based on a lighter weight lifted for multiple reps.
Estimate your one-rep max lift instantly.
This tool estimates your one-repetition maximum (the most weight you could lift for a single rep) based on a lighter weight lifted for multiple reps.
Useful for programming training percentages without needing to test a true 1RM, which carries injury risk.
Input the weight used for your set.
Input how many reps you did with that weight.
The result updates automatically using a standard formula.
The Epley formula, a widely-used method for estimating 1RM from submaximal reps: 1RM = weight × (1 + reps/30).
It provides a reasonable estimate, especially for lower rep ranges - very high rep sets tend to be less accurate for 1RM prediction.
This estimate avoids the injury risk of true 1RM testing - many lifters prefer using estimated 1RM for programming purposes.
No, calculations happen entirely in your browser.
This formula is commonly applied to major compound lifts (squat, bench, deadlift) though the math works for any weighted exercise.
Generally 1-10 reps provide more reliable estimates than very high rep sets.
Training programs often prescribe percentages of 1RM for different training goals (strength, hypertrophy, endurance).
Yes, though as a general guide - beginners' strength can fluctuate more, so periodic reassessment is helpful.
No, this is an estimation tool - consult a qualified trainer for personalized programming guidance.
Yes, completely free with no sign-up required.