A one-rep max (1RM) calculator estimates the maximum weight you can lift for a single repetition based on the weight used and reps performed in a working set.
About this calculator
A one-rep max (1RM) calculator estimates the maximum weight you can lift for a single repetition based on the weight used and reps performed in a working set. Testing true 1RM can be risky; this formula lets you estimate it safely from a submaximal set.
The Epley formula (1RM = Weight × (1 + Reps/30)) is commonly used in strength training programming. Your 1RM anchors your entire strength training program, all percentage-based prescriptions (e.g., 80% of 1RM for 3 sets of 5) are calculated from it.
Common uses
- Calculate 1RM for bench press, squat, or deadlift
- Plan training percentages (65%, 75%, 85% of 1RM) for a program
- Track strength progress over a training cycle
- Find working weights for a 5/3/1 or linear periodisation program
Frequently asked questions
How accurate is the 1RM formula?
The Epley formula is most accurate for rep ranges of 1–10. Above 10 reps, accuracy drops. The formula also tends to slightly overestimate 1RM for trained lifters and underestimate it for beginners. Always approach estimated 1RM attempts cautiously and use a spotter.
What percentage of 1RM should I train at?
General guidelines: 90%+ of 1RM for max strength (1–3 reps). 75–85% for strength (3–6 reps). 65–75% for hypertrophy (6–12 reps). 50–65% for muscular endurance (12–20 reps). These ranges vary by training program and individual goals.