Health & FitnessReviewed Methodology
One Rep Max Calculator
A one rep max calculator helps you estimate your 1RM by using lifted weight and repetitions with a standard strength-training formula.
Health & FitnessReviewed by Editorial Health Review
Quick answer
This estimate uses the Epley 1RM formula.
What this tells you
- •This estimate uses the Epley 1RM formula.
- •Best reliability is typically within lower repetition ranges.
- •Use estimate cautiously and prioritize safe lifting practice.
How to Use
- 1Enter weight lifted and number of reps completed with good form.
- 2Select unit and calculate.
- 3Review estimated 1RM and common training percentages.
How It Works
Formula
Estimated 1RM = lifted weight x (1 + reps/30)The Epley formula provides a practical estimate from submaximal sets and is commonly used for programming.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
1RM estimate example
Weight100 kg
Reps5
ResultEstimated 1RM: 116.67 kg
The formula estimates potential max from a controlled multi-rep effort.
Common mistakes
- Using poor-form sets to estimate max
- Applying estimate to high reps beyond practical formula range
- Treating estimated max as guaranteed safe attempt weight
Limitations
This estimate depends on formula assumptions and lift quality. It does not account for fatigue, technique variation, exercise selection, or injury risk.
Frequently Asked Questions
No. It is a formula-based estimate and real max performance can differ.
Lower rep sets are generally more reliable than very high-rep sets for 1RM estimation.
No. Use safe setup, spotters, and proper progression when attempting heavy lifts.