1RM (One-Rep Max) Strength Calculator
Estimate one-rep max (1RM) using Epley, Brzycki, and Lombardi formulas.
Last reviewed by the Radiatus Cloud team
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Estimate your one-rep max
Your one-rep max is the most you can lift once, and knowing it guides training without the risk of actually testing it. This calculator estimates your 1RM using the Epley, Brzycki and Lombardi formulas.
Why estimate rather than test
Actually attempting a true one-rep max is risky, especially without a spotter, so estimating it from a lighter weight lifted for several reps is the safer, standard approach. The relationship between reps and max is well studied, and several formulas, Epley, Brzycki, Lombardi, capture it slightly differently. Showing all three gives a range rather than a single figure, which is more honest since they disagree a little. Knowing your estimated 1RM lets you set training weights as percentages of it, which is how strength programmes are structured.
A fitness estimate
This is an estimate from a standard formula for general information, not medical advice; individual health depends on far more than any single number, so consult a professional for anything that matters. It runs entirely in your browser, so nothing you enter is uploaded, keeping your figures on your own machine.
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Frequently Asked Questions
What is a one-rep max?
The most weight you can lift for a single repetition. It anchors training weights, often set as percentages of it.
Why estimate rather than test it?
Because attempting a true max is risky, especially without a spotter. Estimating from a lighter weight lifted for several reps is safer and standard.
Why show three formulas?
Because Epley, Brzycki and Lombardi capture the rep-to-max relationship slightly differently. Showing all three gives an honest range rather than false precision.
How do I use my 1RM?
To set training weights as percentages of it, which is how strength programmes prescribe loads for different rep ranges.
Is this medical advice?
No. It is a fitness estimate. Train within your ability and seek guidance for safe lifting.
Privacy & Security
Calculated locally in your browser. Not medical advice. Lift safely.
How to Use
Enter weight and reps to estimate 1RM with multiple formulas.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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