1RM (One Rep Max)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
P × 36/(37-R)
About this calculator
The 1RM (One Rep Max) calculator is a vital tool for athletes and coaches who want to determine an individual's maximum strength in a specific exercise. It estimates the maximum weight that can be lifted in a single repetition, based on the weight lifted and the number of repetitions performed.
The formula used is straightforward: 1RM = Weight × (36/(37-reps)). This means that the more repetitions performed with a given weight, the higher the estimated 1RM. It's essential to note that this is an estimate and may vary depending on the exercise and individual.
The 1RM is commonly used in strength training programs to monitor athlete progress and adjust weights and workloads. It's particularly useful in sports that require explosive strength, such as weightlifting, American football, and rugby.
When using this calculator, it's crucial to ensure the accuracy of the input data, as small errors can significantly impact the 1RM estimate. Additionally, it's essential to remember that 1RM is a measure of maximum strength and should not be used as the sole indicator of performance or progress.
Frequently asked questions
What is 1RM?
1RM is the maximum weight that can be lifted in a single repetition of an exercise.
How is 1RM calculated?
1RM is calculated using the formula: 1RM = Weight × (36/(37-reps)).
Why is 1RM important?
1RM is important for monitoring athlete progress and adjusting weights and workloads in strength training programs.
What are the precautions when using this calculator?
It's crucial to ensure the accuracy of the input data and remember that 1RM is a measure of maximum strength and should not be used as the sole indicator of performance or progress.
In which sports is 1RM most useful?
1RM is particularly useful in sports that require explosive strength, such as weightlifting, American football, and rugby.