One Rep Max Calculator
Estimate 1RM from a submaximal set using Epley, Brzycki and Lombardi formulas.
Inputs
Enter weight in any unit — the result is in the same unit.
Accuracy is highest for 1–10 reps. Beyond 10 reps all formulas become increasingly imprecise.
Estimated 1RM (average)
115.6
Epley
116.7
Brzycki
112.5
Lombardi
117.5
Step by step
Epley
100 × (1 + 5/30)
= 116.7
Brzycki
100 × 36/(37 − 5)
= 112.5
Lombardi
100 × 5^0.1
= 117.5
Average 1RM
(116.7 + 112.5 + 117.5) ÷ 3
= 115.6
Training percentage table (based on average 1RM)
| % of 1RM | Target Weight | Typical Rep Range |
|---|---|---|
| 50 | 57.8 | 15+ |
| 55 | 63.6 | 15+ |
| 60 | 69.4 | 10–15 |
| 65 | 75.1 | 8–12 |
| 70 | 80.9 | 6–10 |
| 75 | 86.7 | 5–8 |
| 80 | 92.5 | 4–6 |
| 85 | 98.3 | 3–5 |
| 90 | 104.0 | 3 |
| 95 | 109.8 | 1–2 |
| 100 | 115.6 | 1–2 |
How it works
One rep max is the gold standard for measuring strength, but testing it directly carries injury risk, especially for beginners. Submaximal testing (lifting a manageable weight for a moderate number of reps) combined with a predictive formula is safer and correlates well with actual 1RM for 1–10 repetitions. The three formulas shown have different mathematical shapes, so their average reduces systematic bias from any single model. Use the resulting 1RM to set training loads: 70–80% for hypertrophy, 80–90% for strength, >90% for maximal strength development.
Formulas
Epley (1985)
1RM = Weight × (1 + Reps/30)
- W
- Weight lifted
- r
- Repetitions completed
Brzycki (1993)
1RM = Weight × 36 / (37 − Reps)
- W
- Weight lifted
- r
- Repetitions completed
Lombardi (1989)
1RM = Weight × Reps^0.1
- W
- Weight lifted
- r
- Repetitions completed
1RM estimates are mathematical predictions, not substitutes for proper progression programming or coaching. Attempting maximum or near-maximum lifts without appropriate training history, technique, and supervision carries injury risk. Always train safely.
Frequently Asked Questions
How many reps should I use for the most accurate estimate?
3–6 reps gives the most accurate prediction. At 1–2 reps the result is almost your actual 1RM. At 10+ reps neural efficiency and muscular endurance become confounding factors, making the estimate less reliable.
Does the unit (kg vs lb) matter?
No — the formula is unit-agnostic. Enter your weight in whatever unit you use and the result will be in the same unit.
Should I attempt my predicted 1RM?
If you're new to heavy lifting, don't. The estimate is a planning tool, not a mandate. Work up to 90–95% of your predicted 1RM for training cycles before testing the actual maximum. Always have a spotter for maximal or near-maximal attempts.