One-Rep Max Calculator
Estimate your 1RM for any lift from a submaximal set, then get training load recommendations for every percentage.
What is the One-Rep Max?
The one-repetition maximum (1RM) is the maximum amount of weight you can lift for one complete repetition with proper form for a given exercise. It is the universal standard for measuring absolute strength in resistance training.
Directly testing your 1RM is safe for experienced lifters but risky for beginners due to the high intensity and injury potential. Submaximal 1RM estimation — lifting a lighter weight for multiple reps and using a prediction formula — allows you to estimate your max without maxing out.
The Epley formula (1985) is the most widely used method: 1RM = weight × (1 + reps ÷ 30). It is most accurate when using 2–10 reps. Accuracy decreases as rep count increases beyond 10, because muscular endurance factors become more significant relative to absolute strength.
Training Load Percentages
Once you know your 1RM, you can programme training at specific intensities to target different training adaptations:
| % of 1RM | Typical Rep Range | Training Goal |
|---|---|---|
| 90–100% | 1–3 reps | Maximal strength |
| 80–90% | 3–5 reps | Strength |
| 70–80% | 6–10 reps | Hypertrophy (muscle growth) |
| 60–70% | 10–15 reps | Hypertrophy / muscular endurance |
| 50–60% | 15–20 reps | Muscular endurance |
| < 50% | 20+ reps | Endurance / warm-up |
Worked Examples
Example 1: Bench press 80 kg × 5 reps.
1RM = 80 × (1 + 5/30) = 80 × 1.167 = 93 kg. 80% of 1RM ≈ 74 kg for 6–10 rep hypertrophy work.
Example 2: Squat 140 lbs × 8 reps.
1RM = 140 × (1 + 8/30) = 140 × 1.267 = 177 lbs. 85% ≈ 150 lbs for strength sets.
Example 3: Deadlift 120 kg × 3 reps.
1RM = 120 × (1 + 3/30) = 120 × 1.1 = 132 kg. Note: using fewer reps gives more accurate estimates.
Frequently Asked Questions
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The Epley formula is one of the most validated and widely used. Other formulas include Brzycki, Lander, and Mayhew. They produce similar results in the 1–10 rep range. The Epley formula tends to slightly overestimate for sets of 10+ reps. For training purposes, any of these formulas is sufficiently accurate.
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Direct 1RM testing is appropriate for experienced lifters who are familiar with maximal effort techniques. Beginners should avoid maximal testing for at least the first 6 months. For most people, submaximal estimation is safer and sufficient for programming purposes.
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With consistent training, significant strength gains can be made in the first 6–12 months. After that, progress slows. Re-test or re-estimate your 1RM every 4–8 weeks during a training block, or after any significant change in training volume, intensity, or body weight.
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It depends on your goal. For maximal strength, 80–90%+ is most effective. For hypertrophy (muscle growth), the 65–80% range for 6–15 reps is well-supported. The key variable is proximity to muscular failure — sets taken to or near failure across a range of intensities appear effective for hypertrophy.
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1RM formulas are population-level averages. Individual differences in fibre type composition, neural efficiency, and lifting technique mean personal predictions can be 5–15% off. Use the estimate as a guide to set training loads, not as a definitive number. Your first test of an actual 1RM will help calibrate the formula for you personally.