One-Rep Max Calculator
Estimate your one-rep max (1RM) from any set — enter the weight and reps you lifted and get your projected max plus a full percentage table for programming your working sets.
| %1RM | Weight (kg) | ~Reps |
|---|---|---|
| 100% | 114.5 | 1 |
| 95% | 109 | 2 |
| 90% | 103 | 4 |
| 85% | 97.5 | 6 |
| 80% | 91.5 | 8 |
| 75% | 86 | 10 |
| 70% | 80 | 12 |
| 65% | 74.5 | 15 |
| 60% | 69 | 18 |
| 55% | 63 | 22 |
| 50% | 57.5 | 25+ |
How it works
Epley
1RM = weight × (1 + reps ÷ 30)
Brzycki
1RM = weight × 36 ÷ (37 − reps)
Which to trust
Both are accurate up to ~10 reps and drift apart on high-rep sets. GainLogger shows both and their average so you can sanity-check the estimate.
Frequently Asked Questions
How accurate is a 1RM calculator?
Rep-max formulas are most accurate at 1–10 reps. Past ~10 reps, fatigue and technique break the linear relationship and the estimate inflates. Use a set of 3–8 reps for the best projection.
What is the Epley formula?
Epley estimates one-rep max as weight × (1 + reps ÷ 30). For 100 kg × 5 reps it projects a 116.7 kg max.
Should I test my true 1RM?
Testing a true max is taxing and higher-risk. An estimated 1RM from a calculator lets you program percentages without a maximal attempt every block.
Hit a new max?
Log it in GainLogger — your PRs and progress charts update automatically. Free on iOS & Android.