One Rep Max Calculator
About the One Rep Max Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition, commonly used to plan training percentages for strength programs.
Formula Used
How It Works
This calculator uses the Epley formula, which estimates 1RM from the weight you lifted and the number of reps you completed before failure.
Step by Step
- Enter the weight you lifted for a set.
- Enter the number of reps you completed with that weight before failure.
- The Epley formula estimates the maximum weight you could lift for one rep.
Worked Example
Example: Bench pressing 80 kg for 5 reps:
1RM = 80 × (1 + 5/30) = 80 × 1.167 = 93.3 kg
Frequently Asked Questions
How accurate is an estimated 1RM?
It's a solid estimate for reps under about 10, but accuracy decreases at higher rep ranges - testing your true 1RM directly is more precise.
Which formula does this use?
The Epley formula: 1RM = weight \u00d7 (1 + reps/30), one of the most widely used strength estimation formulas.
Why do I need my 1RM?
Many strength programs prescribe training weights as a percentage of your 1RM, so knowing it helps you set accurate training loads.