How to use it
Pick your unit
Toggle pounds or kilograms. The number you type is treated as that unit.
Enter weight and reps
Use a set taken close to failure with good form for the best estimate.
Read your numbers
The estimated 1RM and percentage table update instantly as you type.
About the 1RM calculator
Your one-rep max is the most weight you could lift for a single repetition. Testing it directly is risky, so this tool estimates it from a submaximal set. The headline number uses the Epley formula, 1RM = weight × (1 + reps ÷ 30). For sets under 37 reps it also shows the Brzycki estimate, weight × 36 ÷ (37 − reps). Both are most accurate in the 1 to 10 rep range; higher rep counts drift apart. The percentage table then scales your estimated max down to common working intensities so you can plan sets across strength, hypertrophy and endurance zones. This is general training guidance, not medical or coaching advice — load conservatively and stop if anything hurts.
Questions
Is anything uploaded?
No. The calculation runs entirely in your browser and nothing is uploaded or stored.
Why are Epley and Brzycki different?
They are two well-known regression formulas fit to different data. They agree closely at low reps and spread apart as reps climb, so treat the result as an estimate rather than an exact number.
How many reps give the best estimate?
Sets of around 1 to 6 reps taken near failure give the most reliable 1RM estimate. Very high rep sets tend to overstate your true max.