One-rep max (1RM) calculator
Estimate your one-rep max (1RM) from a set performed with a submaximal weight, and get a table of working loads by percentage to plan your workouts. All the calculation happens in your browser.
How it works
This tool uses the Epley formula, one of the most widely used in strength training, to estimate the maximum load you could lift for a single rep (1RM) from a set performed with a lighter weight: 1RM = weight lifted × (1 + reps / 30). The table below then applies percentages of that estimated 1RM to help you set working loads (for example 80% for hypertrophy, 90% and above for pure strength).
Why limit the calculation to 12 reps maximum?
The more reps you do, the less accurate the 1RM estimate becomes: muscular fatigue and endurance come into play beyond 10-12 reps and skew the result. For a reliable estimate, use a set of 1 to 10 reps taken to failure or close to technical failure.
Does the estimated 1RM replace a real max-load test?
No, it is an estimate based on a statistical formula, not a direct measurement. The gap from your true max can vary depending on the exercise, your training level and your technique. This information is provided for informational purposes only and does not replace the advice of a coach or a healthcare professional, especially before attempting a load close to your real max.
The calculation runs entirely in your browser: none of the data you enter is sent to a server.