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One Rep Max Calculator Guide
Estimate your one-rep max (1RM) — the most weight you could lift for a single repetition — from a set you've done at a lighter weight for multiple reps. It's a safer way to gauge maximum strength without attempting a true max lift.
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). This calculator shows both and averages them.
How Do I Calculate My One-Rep Max?
Enter the weight and how many clean reps you completed. For example, 185 lb for 5 reps estimates a 1RM of about 216 lb by the Epley formula. The estimate is most accurate for sets of 1–10 reps.
Using Your 1RM for Training
Many programs prescribe a percentage of your 1RM — for example, 5 reps around 85% or 10 reps around 75%. The percentage table below gives training weights based on your estimated max. Always warm up and use a spotter for heavy lifts.
This is a general estimate for information only, not medical or nutritional advice. Individual needs vary with health, goals, and other factors — talk to a doctor or registered dietitian for guidance specific to you.
Related: Calories Burned, Lean Body Mass, and BMR Calculator.
Frequently Asked Questions
What is a one-rep max?
The maximum weight you can lift for a single repetition of an exercise, a common measure of strength.
How accurate is a 1RM estimate?
Estimates are quite good for sets of 1–10 reps but become less reliable with very high rep counts.
Why use a formula instead of testing?
Estimating from a submaximal set is safer and can be done more often than attempting a true one-rep max.
What percentages should I train at?
It depends on your goal, but the table shows common percentages of your estimated max for different rep ranges.
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