One Rep Max Calculator
Estimate your 1RM (one repetition maximum) for any lift using weight and reps performed. Calculate training percentages for programming.
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How to use this calculator
w = weight lifted; r = number of reps completed with that weight. Most accurate for 2–10 reps.
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Enter the weight you lifted and how many reps you completed with that weight.
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The Epley formula estimates your one-rep maximum.
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Use the percentage table for programming: 75–85% for hypertrophy sets, 85–95% for strength.
Frequently asked questions
How accurate is the 1RM estimate?
The Epley formula is most accurate for 2–10 reps. Accuracy decreases for high-rep sets (>15) because factors like muscular endurance play a larger role. For best results, test with a weight you can lift 3–8 times.
What percentage of 1RM should I train at?
55–65% for muscular endurance (15+ reps); 67–85% for hypertrophy (8–15 reps); 85–95% for strength (1–5 reps); 95–100% for maximal strength/power work.
Should I actually attempt a true 1RM?
Only with proper technique, warm-up, and a spotter. For most training purposes, estimating 1RM from a submaximal lift is safer and sufficient for programming.
1RM Calculator — One Rep Max & Training Percentages
How to use the one rep max
Use this one rep max to your 1rm (one repetition maximum) for any lift using weight and reps performed. Enter your values above and get your result in seconds. The tool is free, works on all devices, and keeps your data private — nothing is stored or shared.
How the one rep max works
The one rep max calculator uses standard formulas used in health tracking, fitness planning, and wellness management. Enter your inputs, and the tool calculates the result instantly in your browser. No server-side processing means your data stays on your device. Results update in real time as you change inputs.
Why 1RM matters for strength programming
Percentage-based training anchors every working set to your maximum strength. Without knowing your 1RM, you can't precisely control training intensity. Most powerlifting, Olympic lifting, and strength-focused programs (5/3/1, Westside, Texas Method) are built around 1RM percentages.
Epley vs other 1RM formulas
Several formulas exist: Epley (1 + r/30), Brzycki (36 / (37 − r)), and Lander (1 / (1.013 − 0.0267123 × r)). They produce similar results for moderate reps. Our calculator uses Epley because it tends to perform well across a wide rep range and is most widely used in sports science literature.
One rep max: how it works
This free tool provides a quick, evidence-based estimate for wellness planning. It uses standard formulas accepted by health professionals worldwide. Enter your measurements for an instant result — always follow up with a qualified practitioner for personal guidance.
Who uses this tool?
Athletes, fitness enthusiasts, nurses, and anyone monitoring their health use it as a starting point for wellness decisions. Share the output with your doctor or dietitian for a professional interpretation.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →