One Rep Max Calculator
Estimate your one repetition maximum (1RM) using 7 proven strength formulas. Enter the weight you lifted and how many reps you performed.
Rep % Reference
| Reps | % of 1RM | Target Weight |
|---|---|---|
| 1 | 100% | — |
| 2 | 95% | — |
| 3 | 93% | — |
| 4 | 90% | — |
| 5 | 87% | — |
| 6 | 85% | — |
| 7 | 83% | — |
| 8 | 80% | — |
| 9 | 77% | — |
| 10 | 75% | — |
| 12 | 70% | — |
| 15 | 65% | — |
For informational purposes only. Always warm up thoroughly and use a spotter when lifting heavy weights.
Frequently Asked Questions
One rep max (1RM) is the maximum amount of weight you can lift for a single repetition of any given exercise. It is the foundation of strength programming — coaches and athletes use percentages of 1RM to prescribe training loads with precision. For example, 70–80% of 1RM targets hypertrophy, while 85–95% builds maximal strength. Knowing your 1RM lets you follow structured programs like 5/3/1, Starting Strength, or Conjugate without guessing on weights.
No single formula is universally best — accuracy depends on the individual and the number of reps used. The Epley and Brzycki formulas are the most widely used and perform well for 2–10 reps. Mayhew and Wathan tend to be more accurate at higher rep ranges (8–12). All formulas lose accuracy beyond 10 reps because the relationship between reps and maximum strength becomes less predictable. For the best estimate, test with 3–5 reps at a challenging but manageable weight.
Direct 1RM testing is safe when done correctly, but requires preparation. Always begin with a thorough warm-up: start with the bar, then add weight in incremental jumps (60%, 75%, 85%, 95% of expected max) with 3–5 minutes rest between sets. Use a spotter or safety bars on squats and bench press. Avoid direct 1RM testing if you are a beginner (less than 6 months of consistent training), injured, or fatigued. Using this calculator to estimate your 1RM from a sub-maximal set is often safer and sufficient for programming.
Training percentages map to different goals: 60–70% of 1RM for muscular endurance (12–20 reps), 70–80% for hypertrophy (8–12 reps), 80–90% for strength (3–6 reps), and 90–100% for maximal strength and peaking (1–3 reps). Popular programs like Wendler 5/3/1 cycle through 65%, 75%, and 85% waves over 3 weeks before a deload. The rep % reference table in this calculator shows the standard percentage for each rep count so you can quickly plan your working sets.