One-Rep Max Calculator
Estimate your 1RM from any rep range
Enter the number of reps you completed (max 30)
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise. This free calculator uses the Epley formula to estimate your 1RM from any weight and rep combination, plus a percentage chart for programming training loads.
How This Is Calculated
This calculator uses three well-established prediction formulas. The Epley formula (1985) is the most commonly used in strength training. The Brzycki formula (1993) tends to be more accurate for lower rep ranges (1-10). The Lombardi formula provides an additional reference point. We show all three for transparency.
Epley: 1RM = weight × (1 + reps/30)
Brzycki: 1RM = weight × (36 / (37 − reps))
Lombardi: 1RM = weight × reps^0.10
Assumptions & Limitations
1RM predictions become less accurate beyond 10 reps. These formulas were developed primarily with compound barbell lifts (squat, bench, deadlift) and may be less accurate for isolation exercises or machine-based movements. Factors like fatigue, technique breakdown, and training experience affect real-world maxes. Never attempt a true 1RM without proper supervision and warm-up.
What To Do With These Numbers
Use your estimated 1RM to program training loads. Common rep schemes: 85-95% of 1RM for strength (1-5 reps), 65-80% for hypertrophy (6-12 reps), 50-65% for endurance (12+ reps). Re-test every 4-8 weeks to track progress and adjust your training weights.
Scientific References
- Epley B. Poundage Chart. Boyd Epley Workout. 1985.
- Brzycki M. Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue. JOPERD. 1993;64(1):88-90.
Frequently Asked Questions
How do I calculate my one-rep max without actually lifting it?
Use the Epley formula: multiply your weight lifted by (1 + reps/30). For example, if you bench 185 lbs for 5 reps, your estimated 1RM is 185 × (1 + 5/30) = 216 lbs. This is safer and more practical than actual 1RM testing.
Is the Epley formula accurate?
The Epley formula is accurate within 5-10% for sets of 1-10 reps. Accuracy decreases with higher rep ranges (15+). For the best estimate, use a weight you can lift for 3-6 reps with good form.
How often should I test my one-rep max?
Most lifters should estimate their 1RM using submaximal formulas rather than testing it directly. If you do test, every 8-12 weeks is sufficient. Frequent 1RM testing increases injury risk and provides minimal additional training benefit.
What percentage of 1RM should I train at?
For strength: 80-90% of 1RM for 1-5 reps. For hypertrophy (muscle size): 65-80% for 6-12 reps. For muscular endurance: 50-65% for 12-20 reps. Most programs use a combination across training phases.
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Disclaimer
The information provided on this page is for educational and informational purposes only. These calculations are estimates based on population averages and may not reflect your individual needs. Consult a qualified healthcare professional before starting any diet or exercise program.
Last reviewed: February 14, 2026