One Rep Max Calculator
Estimate maximum weight for one repetition from reps and weight.
Lift Details
Estimated 1RM: lbs
Training Percentages:
- 90% (1-2 reps): lbs
- 80% (3-5 reps): lbs
- 70% (6-8 reps): lbs
- 60% (9-12 reps): lbs
The Epley formula
This calculator uses the Epley formula: 1RM = weight × (1 + 0.0333 × reps). It's one of several popular estimation formulas (others include Brzycki and Lombardi) that predict your one-rep max from a lighter set taken close to failure, without needing to actually attempt a maximal single lift.
Frequently asked questions
How accurate is an estimated 1RM? It's reasonably accurate for sets of about 2–10 reps performed close to failure, but accuracy drops for very high-rep sets (15+) since fatigue and technique breakdown affect the estimate more at high rep counts.
Why do the training percentages matter? Many strength programs prescribe work sets as a percentage of 1RM (e.g., "work up to 80% for 5 reps") — knowing your estimated max lets you calculate the actual weight to load for a given percentage and target rep range.
Should I actually test my true 1RM? Testing a true 1RM carries more injury risk and requires a spotter and warm-up protocol — for most training purposes, an estimated 1RM from a submaximal set is safer and sufficiently accurate for programming.