How do I use the One Rep Max Calculator?

Enter your values in the input fields and the One Rep Max Calculator will automatically calculate results in real-time. All calculations are performed instantly in your browser.

Is the One Rep Max Calculator free to use?

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One Rep Max Calculator

Estimate your 1RM based on reps performed. Uses the Epley formula.

Logic Verified

Configure parametersUpdated: Feb 2026

Weight Lifted (lbs) - 100

Reps Performed - 100

Estimated 1 Rep Max

90% (Heavy Training)

80% (Hypertrophy)

Expert Analysis & Methodology

Strategic Optimization

Based on your inputs, small adjustments in Weight Lifted (lbs) could improve your outcome significantly.

One Rep Max (1RM) Calculator

Estimate the maximum weight you can lift for a single repetition based on your sub-maximal lifts. Uses the Epley Formula.

Why calculate 1RM?

Safety: Attempting a true 1RM test can be dangerous without spotters. This estimator allows you to test your strength safely using lighter weights.
Programming (Percent Based Training): Many programs (like 5/3/1) require you to lift a percentage of your 1RM (e.g., "Do 3 sets at 80% of 1RM").

The Epley Formula

We use the most popular formula: 1RM = Weight * (1 + Reps/30).

Note: Accuracy decreases as reps increase. For best results, use a weight you can lift 3-5 times.

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Disclaimer

This calculator is provided for educational and informational purposes only. It does not constitute professional legal, financial, medical, or engineering advice. While we strive for accuracy, results are estimates based on the inputs provided and should not be relied upon for making significant decisions. Please consult a qualified professional (lawyer, accountant, doctor, etc.) to verify your specific situation. CalculateThis.ai disclaims any liability for damages resulting from the use of this tool.