Science-backed fitness intelligence
About the One Rep Max Calculator
A one rep max is the greatest weight you can lift once with good form for a specific exercise. It helps lifters track strength and choose suitable training loads.
What is a one rep max (1RM)?
A one rep max is the greatest weight you can lift once with good form for a specific exercise. It helps lifters track strength and choose suitable training loads.
Using your results
Every calculated 1RM is an estimate. Use the range as a training guide, and choose working weights that match your experience, technique, and current condition.
How the calculators work
The calculator compares five established formulas to give you a useful range of 1RM estimates:
- Epley formula: A widely used formula that gives reliable estimates across common repetition ranges.
- Brzycki formula: A popular formula that is especially useful for sets of ten repetitions or fewer.
- McGlothin formula: An alternative estimate that uses a different repetition adjustment.
- Lombardi formula: An exponential calculation often used by strength athletes.
- O'Conner formula: A simple calculation that provides a practical comparison with the other estimates.
Safety tips
- Warm up thoroughly before attempting heavy lifts.
- Use controlled movement and proper technique.
- Use a spotter or safety equipment for near-maximal lifts.
- Increase the load gradually to reduce injury risk.
- Stop if you feel pain and allow enough time for recovery.
How this page is built
Built by WillyEvery calculator here is designed to be practical, fast, and easy to trust. Use the tools for planning, not guessing.