Estimate your 1RM safely from submaximal sets using published Brzycki, Epley, and Lander formulas. NSCA training zone chart included.
Enter a weight and rep count (2-10 reps for best accuracy) to estimate your one-rep max using Brzycki, Epley, and Lander formulas. According to NSCA guidelines, training at 67-85% of 1RM builds muscle size, while 85-100% builds maximum strength. 3-5 rep sets produce the most reliable estimates per published validation research.
Written by Ash K · Last updated: June 2026 · Sources cited below
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. This calculator estimates it from a lighter weight and rep count — so you don't need to actually attempt a dangerous maximal lift.
Enter the weight you lifted and how many reps you completed. The calculator applies multiple validated formulas (Epley, Brzycki, Lombardi) and shows the average estimate.
Key Takeaway: 1RM is estimated from submaximal lifts using validated formulas. The most common: Epley formula = weight × (1 + reps/30). Most accurate with 3–10 reps. Above 10 reps, accuracy decreases. Never attempt an actual 1RM without a spotter and proper warm-up.
The Epley Formula: 1RM = weight × (1 + reps ÷ 30)
Example: Bench press 185 lbs × 6 reps → 185 × (1 + 6/30) = 185 × 1.20 = 222 lbs estimated 1RM
| Formula | Equation | Best for |
|---|---|---|
| Epley | w × (1 + r/30) | General use, most popular |
| Brzycki | w × 36/(37 − r) | Lower rep ranges (1–6) |
| Lombardi | w × r^0.1 | Moderate rep ranges |
| O'Conner | w × (1 + 0.025 × r) | Conservative estimate |
| % of 1RM | Reps | Training Goal |
|---|---|---|
| 90–100% | 1–3 | Maximal strength |
| 80–89% | 4–6 | Strength + size |
| 70–79% | 7–10 | Hypertrophy (muscle growth) |
| 60–69% | 11–15 | Muscular endurance |
| Below 60% | 15+ | Endurance / warm-up |
Tip: Recalculate your 1RM every 4–6 weeks to track strength progress and adjust training loads. A 5 lb increase in estimated 1RM over 4 weeks represents meaningful strength gain.
Warning: Actually attempting a true 1RM carries injury risk — especially for bench press, squat, and overhead press. Always use a spotter for maximal attempts. Calculator estimates from 3–5 rep sets are safer and nearly as accurate as actual max testing.
For nutrition to support strength gains, see our macro calculator and protein intake calculator.
Bottom Line: Estimate your 1RM from submaximal lifts using the Epley or Brzycki formula. Use it to set training percentages. Recalculate monthly. Don't actually attempt a true 1RM without a spotter — the calculator is safer and nearly as accurate.
How do I calculate my one rep max?
Use the Epley formula: 1RM = weight × (1 + reps/30). Example: 200 lbs × 5 reps → 200 × 1.167 = 233 lbs. Or use this calculator which averages multiple formulas.
Is the 1RM calculator accurate?
Within ±5% for 3–10 rep sets. Accuracy decreases above 10 reps. The estimate is best used for setting training percentages, not for determining exact maximal capacity.
How often should I test my 1RM?
Recalculate every 4–6 weeks. You don't need to actually max out — just log a heavy set of 3–6 reps and let the calculator estimate.
Training Zones by % of 1RM — NSCA Guidelines
This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider with questions about your health.