One Rep Max Calculator
Enter the weight you lifted and how many reps you completed to estimate your one-rep max (1RM).
Last updated: September 5, 2026
Frequently asked questions
What's the formula for estimating one-rep max?
The Epley formula: 1RM = weight × (1 + reps ÷ 30). Lifting 185 lb for 5 reps estimates a one-rep max of about 216 lb.
Why use percentages of 1RM for training?
Training programs often prescribe a percentage of your 1RM (like 80% for strength work) to target specific adaptations - knowing your estimated max lets you calculate the right weight for any given percentage.
How accurate are 1RM formulas for very low or very high rep counts?
They're most accurate in the 2-10 rep range - estimates from sets of 1-2 reps are close to the true max by definition, but formulas become progressively less reliable above about 12 reps, since fatigue and endurance start to matter more than pure strength.
Should I test my actual 1RM or rely on the calculated estimate?
For most training purposes, a calculated estimate from a lower-rep set is safer and sufficient, since testing a true 1RM carries higher injury risk and requires a proper warm-up and spotter. Estimates are most accurate in the 3-8 rep range and less reliable below 3 or above 12 reps.
What's an example one-rep max calculation?
Squatting 225 lb for 8 reps: 1RM = 225 × (1 + 8 ÷ 30) ≈ 285 lb using the Epley formula.
How does the Epley formula compare to other 1RM formulas like Brzycki?
Different formulas (Epley, Brzycki, Lombardi) give slightly different estimates for the same weight and reps, usually within a few pounds of each other - Epley tends to estimate a bit higher at higher rep counts, but all are approximations rather than exact predictions.
Can I use my estimated 1RM to plan a workout program?
Yes - many strength programs prescribe training weights as a percentage of your 1RM (e.g., 5 sets at 75% of 1RM). Multiply your estimated max by the target percentage to find the weight to load - just re-test periodically since your true max changes as you train.