Printed on 2/13/2026
For informational purposes only. This is not medical advice.
The one-repetition maximum (1RM) is the maximum weight you can lift for a single repetition with proper form. Rather than testing your actual 1RM (which carries injury risk), you can estimate it from a submaximal lift. This calculator uses three established prediction formulas to give you a range of estimated maxes.
Formula: Epley: 1RM = weight × (1 + reps/30)
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
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1RM prediction formulas are most accurate for 1–10 reps, with accuracy decreasing as rep count increases. They typically have an error margin of 5–10%. For the most accurate estimate, use a weight you can lift for 3–5 reps. The formulas assume reps are performed to failure with good form.
No single formula is universally best. Epley is the most popular and works well across rep ranges. Brzycki tends to be more conservative and closely matches Epley at lower reps. Using multiple formulas gives a realistic range. Choose the one that most closely matches your tested maxes.
Testing a true 1RM carries injury risk and should only be done with proper warm-up, a spotter, and good technique. For most training purposes, estimating from submaximal lifts is safer and sufficient. Competitive powerlifters and weightlifters may need to test actual maxes for competition preparation.
Common training percentages: 60–70% of 1RM for muscular endurance (12–15 reps), 70–85% for hypertrophy (6–12 reps), and 85–95% for strength (1–5 reps). Many programs (like 5/3/1 or Starting Strength) base their progression on a training max, typically 85–90% of your estimated 1RM.