Key Takeaways
- Your 8RM (Eight Repetition Maximum) is approximately 78.6% of your 1RM, placing it squarely in the hypertrophy (muscle-building) rep range.[1]
- This calculator uses 6 validated prediction formulas (Epley, Brzycki, Lombardi, Lander, Mayhew, Wathan) and averages them for improved accuracy.[2]
- Prediction accuracy is highest when input reps are in the 3–6 range and decreases with higher rep counts (10+).[3]
- The 8RM is a practical training weight for hypertrophy programs — 3–4 sets of 8 reps provides optimal mechanical tension and metabolic stress for muscle growth.
What is 8RM and Why Does It Matter?
Your 8RM is the maximum weight you can lift for exactly 8 repetitions with proper form. It represents approximately 78.6% of your one-repetition maximum (1RM) based on the NSCA rep-percentage relationship.[1]
The 8-rep range sits at the intersection of strength and hypertrophy training. It provides sufficient mechanical tension to stimulate muscle growth while allowing enough volume (sets × reps) to create the metabolic stress that drives hypertrophy adaptations.
Knowing your 8RM is especially useful for:
- Programming hypertrophy blocks (typically 3–4 sets of 6–10 reps)
- Establishing a baseline for progressive overload
- Periodizing between strength phases (1–5 reps) and hypertrophy phases (6–12 reps)
- Warm-up planning — the warm-up protocol above progressively loads to your 8RM working weight
For other rep max calculations, see our 1RM Calculator, 5RM Calculator, and 10RM Calculator.
The 6 Prediction Formulas Explained
Each formula uses a different mathematical model to estimate your 1RM from a submaximal lift. Averaging all six reduces the bias of any single formula:[2]
- Epley: 1RM = weight × (1 + reps/30). Linear model, widely cited. Tends to slightly overestimate at high rep counts.
- Brzycki: 1RM = weight × 36/(37 − reps). Most accurate for compound movements in the 5–10 rep range.[3]
- Lombardi: 1RM = weight × reps^0.1. Uses an exponential relationship, producing moderate estimates.
- Lander: 1RM = 100 × weight / (101.3 − 2.67 × reps). Regression-based, good for moderate rep ranges.
- Mayhew: 1RM = 100 × weight / (52.2 + 41.9 × e^(−0.055 × reps)). Exponential decay model.
- Wathan: 1RM = 100 × weight / (48.8 + 53.8 × e^(−0.075 × reps)). Similar to Mayhew with different coefficients.
8RM vs Other Rep Maxes
| Rep Max | % of 1RM | Primary Adaptation | Typical Programming |
|---|---|---|---|
| 1RM | 100% | Maximal Strength | 1–3 sets × 1 rep, 3–5 min rest |
| 3RM | 93.3% | Strength | 3–5 sets × 3 reps, 3–5 min rest |
| 5RM | 86.7% | Strength / Power | 3–5 sets × 5 reps, 2–4 min rest |
| 8RM | 78.6% | Hypertrophy | 3–4 sets × 8 reps, 90s–2 min rest |
| 10RM | 74.4% | Hypertrophy / Endurance | 3–4 sets × 10 reps, 60–90s rest |
| 15RM | 67.5% | Muscular Endurance | 2–3 sets × 15 reps, 30–60s rest |
How to Use Your 8RM for Programming
Once you know your 8RM, apply it to structured hypertrophy programming:
- Standard hypertrophy: 3–4 sets of 8 reps at your 8RM, with 90–120 seconds rest between sets
- RPE alignment: Your 8RM at true maximal effort corresponds to RPE 10. For sustainable training, work at RPE 8–9 (2–1 reps in reserve)
- Progressive overload: When you can complete 4 sets of 8 reps at RPE 8, increase weight by 2.5 kg (5 lbs) the following session
- Periodization: Alternate between 8RM-focused blocks (4–6 weeks) and heavier strength blocks (3–5 reps) for optimal long-term development
For comprehensive volume and intensity programming, use our Training Volume Calculator and Progressive Overload Calculator.
Accuracy Considerations
All rep-max prediction formulas have inherent limitations:[4]
- Predictions are most accurate when using 3–6 rep input sets
- Accuracy decreases significantly above 10 reps
- Individual factors (fiber type distribution, exercise technique, training history) create ±5–10% variation
- Machine exercises may predict differently than free-weight compound movements
- The formula spread (shown in results) indicates prediction uncertainty — smaller spread = higher confidence
Frequently Asked Questions
Sources & References
- Prediction of One Repetition Maximum Strength: Validity of Different Prediction Equations. LeSuer DA et al.. PMC / National Library of Medicine (1997)
- Prediction of 1-RM Strength from a 4-6 RM and a 7-10 RM Submaximal Strength Test. Dohoney P et al.. ResearchGate (2002)
- Accuracy of Prediction Equations for One-Repetition Maximum. Various. PMC (2024)
- Repetition Maximum Prediction: A Systematic Review. Various. ScienceDirect (2024)
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NASM-certified fitness and nutrition coach with over 10 years of hands-on experience helping people build strength, lose fat, and live healthier lives. Specializing in gym-based workouts with a strong focus on lifting technique, biomechanics, and practical exercise science. Through FitLifeRegime, sharing the tools, tips, and insights that have worked for hundreds of clients — helping you start your own fitness journey with confidence and clarity.
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Certified Personal Trainer & Sports Nutritionist from the National Academy of Sports Medicine
This tool is for informational and journaling purposes only.
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