One Rep Max Calculator
Estimate the most you could lift for a single rep, from a weight and the reps you managed with it. No need to test a true max.
Your details
Your results
Enter the weight and reps of a hard set to see your estimated one rep max.
Estimated one rep max
Average of the two estimates below.
Above 10 reps the estimate gets less reliable. A set of 3 to 10 reps gives a better number.
- Epley estimate
- Brzycki estimate
| % of 1RM | Weight | Reps (about) |
|---|---|---|
| 100% | ||
| 95% | ||
| 90% | ||
| 85% | ||
| 80% | ||
| 75% | ||
| 70% | ||
| 65% | ||
| 60% | ||
| 55% | ||
| 50% |
How to use it
- Pick a set you took close to failure, ideally 3 to 10 reps. A recent working set is fine.
- Enter the weight on the bar (or machine) and the number of clean reps.
- Read your estimated one rep max. The table shows training weights at common percentages of it, rounded to plates you can load.
How it's calculated
The calculator uses two published formulas. In both, w is the weight you lifted and r is the number of reps.
- Epley (1985): 1RM = w × (1 + r ÷ 30)
- Brzycki (1993): 1RM = w × 36 ÷ (37 − r)
Example: 100 kg for 5 reps gives 116.7 kg with Epley and 112.5 kg with Brzycki. The main result is the average of the two: 114.6 kg. A single rep counts as your one rep max, so both formulas return the weight itself.
Both formulas assume the set was close to failure. They are most accurate at 10 reps or fewer; above that, the estimate drifts more from a tested max. The calculator accepts up to 15 reps and shows a warning above 10.
The percentage table uses the Epley formula solved for reps (reps = 30 × (100 ÷ percent − 1)) to show roughly how many reps you could do at each percentage. Weights are rounded to 2.5 kg or 5 lb, so you can load them with standard plates.
Sources
- Epley, B. (1985). Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises.
- Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88–90.
- LeSuer, D. A., McCormick, J. H., Mayhew, J. L., Wasserstein, R. L., & Arnold, M. D. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 11(4), 211–213.
Questions
Is an estimated 1RM accurate?
It's a good estimate, not a guarantee. It's closest for sets of 10 reps or fewer taken near failure, and for lifters who train that lift regularly. Your real max on a given day also depends on sleep, warm-up and technique.
Why two formulas?
Epley and Brzycki are two of the most widely used formulas. They give the same result at 10 reps and drift apart slightly below and above that. The calculator shows the average as the main number and both results underneath.
Can I use it for any exercise?
Yes, for any lift where you load a weight and count reps, such as squats, deadlifts, presses and rows. It works less well for bodyweight exercises, where the load isn't just the weight you add.
Should I test my real one rep max?
You don't have to. Many programs only need an estimate to set training weights. If you do test a max, warm up well, use a spotter or safety bars, and only do it on lifts you can perform with solid technique.
Updated October 24, 2026.