What Is a One Rep Max?
Your 1 Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is the standard measure of absolute strength in powerlifting and strength training. Because actually testing your 1RM carries injury risk (especially for beginners), these formulas provide safe estimates from submaximal efforts.
The most accurate estimates come from sets of 3–6 reps at a weight where you could not complete another rep with good form. Beyond 10 reps, the estimates become less reliable due to greater individual variation in strength endurance.
1RM Estimation Formulas
Epley: 1RM = Weight × (1 + Reps/30)
Brzycki: 1RM = Weight × 36 / (37 − Reps)
Lander: 1RM = Weight × 100 / (101.3 − 2.67123 × Reps)
O'Conner: 1RM = Weight × (1 + Reps/40)
Training Zone Reference
| % of 1RM | Approx. Reps | Primary Goal |
|---|---|---|
| 90–100% | 1–3 | Maximum strength, neural adaptation |
| 80–90% | 3–6 | Strength and power |
| 70–80% | 6–12 | Hypertrophy (muscle growth) |
| 60–70% | 12–20 | Muscular endurance |
| Below 60% | 20+ | Endurance, rehab, warm-up |
Frequently Asked Questions
These formulas are accurate within ±5–10% for most people using 3–10 rep sets. Accuracy decreases with higher rep counts (above 10 reps). Individual differences in fiber type composition, training history, and fatigue resistance affect results. The Epley and Brzycki formulas are most validated and widely used.
For intermediate and advanced lifters who regularly train heavy, actual 1RM testing (with a spotter and proper warm-up protocol) is valuable for competition prep and program design. For beginners (under 1 year of consistent training), calculated estimates are safer. Testing a true 1RM requires a specific warm-up protocol of gradually increasing loads.
The 'big three' compound barbell lifts used in powerlifting are: the squat (lower body), bench press (upper body pushing), and deadlift (posterior chain). Total powerlifting score = your 1RM on all three. Elite male powerlifters in the 83kg class total 700+ kg across the three lifts.
Percentage-based programming uses your 1RM to prescribe training weights. A common strength program might prescribe 3×5 at 80% 1RM. If your bench press 1RM is 100kg, you'd lift 80kg for 3 sets of 5. This approach provides consistent, progressive overload. Update your 1RM estimate every 4–8 weeks as you get stronger.