One Rep Max (1RM) Calculator
Estimate your one-rep max from any weight and rep count using the Epley and Brzycki formulas, plus a full training percentage table.
*Estimates only. Actual 1RM varies by individual fatigue, technique, and muscle fiber type. Not medical advice — train within your ability and use a spotter for heavy attempts.
Want to check your recovery capacity between heavy sessions?
Heart Rate Zone Calculator🏋️ Programming With Your 1RM
Once you know your estimated max, you can plan every training block around it.
How it Works
Enter the weight and reps from a recent set taken close to failure. Two proven regression formulas estimate what you could lift for a single rep at full effort.
The Formula
Epley: 1RM = Weight × (1 + Reps/30). Brzycki: 1RM = Weight × 36 / (37 − Reps).
Pro Tip
Use sets of 3-6 reps for the most reliable estimate. Sets taken to true failure at very high reps (15+) tend to underestimate true strength due to fatigue and endurance limits.
Frequently Asked Questions
What is a one-rep max (1RM)? +
Your one-rep max is the heaviest weight you can lift for a single complete repetition of an exercise with proper form. It's the standard reference point for programming training percentages in strength sports like powerlifting and bodybuilding.
What is the Epley formula? +
The Epley formula estimates 1RM as: Weight × (1 + Reps/30). For example, lifting 200 lbs for 5 reps gives an estimated 1RM of 200 × (1 + 5/30) = 233 lbs. It tends to be more accurate for higher rep ranges (above 10 reps).
What is the Brzycki formula and how does it differ from Epley? +
The Brzycki formula is: Weight × 36 / (37 - Reps). It tends to be more accurate for lower rep ranges (under 10 reps) but becomes unreliable or undefined above 36 reps. Using both formulas together and averaging gives a reasonable sanity check.
Should I actually test my true 1RM? +
Formula-based estimates are useful for programming but aren't a substitute for periodic max-effort testing if your goal is competition performance. True 1RM testing carries higher injury risk and requires a spotter, proper warm-up, and technical proficiency — most lifters only test a handful of times per year.
How do I use %1RM for training programs? +
Strength programs prescribe intensity as a percentage of 1RM: roughly 85-100% for max strength (1-5 reps), 67-85% for hypertrophy (6-12 reps), and below 67% for muscular endurance (12+ reps). Once you know your estimated 1RM, multiply by the target percentage to find your training weight.
Why do rep-max estimates get less accurate at high reps? +
Both formulas assume a fairly linear relationship between reps and fatigue, which breaks down past about 10-12 reps due to muscular endurance and metabolic factors becoming more dominant than raw strength. For sets over 10-12 reps, treat the estimate as a rough ballpark rather than a precise number.