One Rep Max Calculator
Estimate 1RM using Epley and Brzycki formulas.
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How This One Rep Max Calculator Works
This calculator uses established scientific formulas validated in peer-reviewed literature. All calculations run locally in your browser — no data is sent to any server.
Percentage-Based Training Zones
| % of 1RM | Reps | Training Goal |
|---|---|---|
| 90 – 100% | 1 – 3 | Maximal Strength |
| 80 – 89% | 3 – 5 | Strength |
| 65 – 79% | 8 – 12 | Hypertrophy (muscle growth) |
| 50 – 64% | 15 – 20 | Muscular Endurance |
| 30 – 49% | 20+ | Power / Speed (explosive) |
Programming With Your 1RM
Once you know your estimated 1RM, program training loads using percentages. The chart above shows your estimated weight for each rep range. For hypertrophy, work at 65–80% for 8–12 reps. For strength, 80–90% for 3–5 reps. Re-test every 4–8 weeks as you progress.
Support strength gains with adequate protein (1.6–2.2g/kg), sufficient calories (eat at or above TDEE), and proper sleep. Monitor training intensity with the Target Heart Rate Calculator on conditioning days.
The Epley vs Brzycki Debate
The Epley formula (1RM = weight × (1 + reps/30)) and Brzycki formula (1RM = weight × 36/(37 - reps)) are the two most widely cited 1RM prediction equations. Research published in the Journal of Strength and Conditioning Research found that both formulas are accurate within 5% for rep counts of 1-10, but accuracy decreases significantly above 10 reps. The Epley formula tends to overestimate at higher rep ranges, while Brzycki tends to underestimate. Our calculator averages both for the most reliable estimate.
Using 1RM for Periodization
Modern strength programs cycle through different intensity zones over weeks or months, a practice called periodization. A typical 12-week program might structure as follows: Weeks 1-4 (hypertrophy): 65-75% of 1RM for 8-12 reps. Weeks 5-8 (strength): 80-90% of 1RM for 3-6 reps. Weeks 9-12 (power/peak): 85-95% of 1RM for 1-3 reps. Re-test your 1RM at the end of each cycle to track progress and adjust loads.
Recovery between heavy sessions is critical. Monitor your heart rate recovery — a resting HR elevated 5+ beats above baseline suggests incomplete recovery. Fuel recovery with adequate calories (eat at or above TDEE during strength phases), protein (1.6-2.2g/kg), and sleep (7-9 hours — the primary window for growth hormone release and muscle repair).
Frequently Asked Questions
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