One Rep Max Calculator
Estimate your 1RM from a weight and reps, with a percentage training table.
Results update as you type.
About this calculator
A one-rep-max (1RM) calculator estimates the most weight you could lift for a single repetition from a set you actually performed. It uses the Epley formula (1RM = w × (1 + reps/30)) by default, with the Brzycki formula as an option, and prints a table of training loads at common percentages of your max.
Frequently asked questions
How is one-rep max estimated?
From a set you completed. The Epley formula is 1RM = weight × (1 + reps ÷ 30); Brzycki is weight × 36 ÷ (37 − reps). Both are accurate for about 2–10 reps and diverge for very high-rep sets.
Why show percentages of my 1RM?
Strength programs prescribe loads as a percentage of your max — for example 5 reps near 85% or hypertrophy work around 70%. The table converts your estimated 1RM into those working weights.
Is estimating safer than testing a true max?
Usually yes. A calculated 1RM from a moderate set avoids the injury risk of grinding out a genuine single, especially without a spotter or experience.
Results are estimates for general guidance only, not financial, medical or tax advice.