How to Calculate Your One-Rep Max (1RM)
Updated June 2026
Estimate your 1RM for any lift.
Your one-rep max (1RM) is the most you can lift for a single rep. You don't need to actually max out to estimate it — a formula does it from a normal set.
The formulas
Two trusted estimates (the calculator averages them):
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Worked example
You bench 100 lb for 5 reps. Epley: 100 × (1 + 5/30) = 116.7. Brzycki: 100 × 36/32 = 112.5. Average ≈ 115 lb estimated 1RM.
Why it matters: percentage training
Most strength programs prescribe a percentage of your 1RM. Once you know it, you can set working weights:
| % of 1RM | Typical use |
|---|---|
| 90–100% | Strength / heavy singles |
| 75–85% | Main strength work (3–6 reps) |
| 65–75% | Hypertrophy (8–12 reps) |
A safety note
Estimates are most accurate at 10 reps or fewer. Always warm up, use a spotter for heavy lifts, and treat the number as a guide, not a guarantee.
Estimate your 1RM for any lift.
Frequently asked questions
Do I have to actually lift my max?
No — that's the point. The formula estimates your 1RM from a submaximal set, which is safer than truly maxing out.
How accurate is the estimate?
Quite accurate within about 10 reps. The more reps past that, the rougher the estimate becomes.