Estimated 1RM calculator
An estimated one-rep max (1RM) is the most weight you could lift once, worked out from a set of a few reps. This calculator uses two common formulas: Epley, weight × (1 + reps/30), and Brzycki, weight × 36/(37 − reps). Use a hard set of 10 reps or fewer, because estimates get less reliable with more reps.
Last updated By ArchiFit
| % of 1RM | Weight |
|---|---|
| 95% | 109 |
| 90% | 103 |
| 85% | 97.5 |
| 80% | 91.5 |
| 75% | 86 |
| 70% | 80 |
| 65% | 74.5 |
| 60% | 69 |
Results round to 0.5 kg or 1 lb. One rep returns the weight itself. The calculator runs in your browser and sends nothing.
How are the Epley and Brzycki formulas worked out?
Both formulas scale the weight you lifted by the number of reps you got.
- Epley: 1RM = weight × (1 + 0.0333 × reps), the same as weight × (1 + reps/30). It is attributed to Boyd Epley's 1985 poundage chart and stated in this form in Macarilla et al. (2022).
- Brzycki: 1RM = weight / (1.0278 − 0.0278 × reps), the same as weight × 36/(37 − reps). It comes from Brzycki (1993) and is stated in this form in Beia et al. (2024).
Example: 100 kg for 5 reps gives about 116.7 kg by Epley and 112.5 kg by Brzycki. The two formulas give the same result at 10 reps. Below 10 reps Epley gives the higher estimate, and above 10 Brzycki does.
Which formula is more accurate?
Neither is exact for everyone. LeSuer et al. (1997) tested seven equations on 67 untrained college students. Predicted and actual 1RMs correlated highly (r above 0.95), but for the bench press and squat most equations still missed the actual average, and every equation underestimated the deadlift. Treat any estimate as a starting point, and expect it to vary by lift.
How many reps should the set have?
Fewer is better. In Reynolds et al. (2006), 5-rep-max sets predicted 1RM most accurately, and the authors concluded that no more than 10 reps should be used in linear equations. This calculator accepts up to 12 reps to match the limit ArchiFit uses in its own analysis. A hard set of about 5 reps gave the most accurate predictions in that study.
How do you use percentages of your 1RM?
Programs often prescribe weights as a percentage of 1RM. The American College of Sports Medicine recommends that novice to intermediate lifters train with 60–70% of 1RM for 8–12 reps, and that advanced lifters cycle loads of 80–100% of 1RM to maximize strength (ACSM, 2009). The table above turns your estimate into those weights.
How ArchiFit uses estimated 1RM
ArchiFit's 8-week analysis uses the Epley formula on sets of 12 reps or fewer. It reports a lift's estimate from first day to last when reps rise at the same weight, and flags body parts whose estimate rose more than 5% since you started them. When your best set falls short of your plan's rep range, Epley also sets the lighter weight to try next. The full method lists every rule.
More guides: progressive overload when you train alone, rep ranges and splits, and all guides.
General fitness information, not medical advice.