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One Rep Max Calculator

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

Decision summary

One Rep Max Calculator estimates Estimated 1 Rep Max, 90% (Heavy Training), 80% (Hypertrophy) from Weight Lifted (lbs), Reps Performed. Use it as a directional estimate, then verify current quotes, rates, rules, or professional advice before acting.

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Change these first: Weight Lifted (lbs), Reps Performed.
Watch these outputs: Estimated 1 Rep Max, 90% (Heavy Training), 80% (Hypertrophy).
Sanity check: compare at least two scenarios before using the estimate for a quote, purchase, or planning decision.
One Rep Max Calculator
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Configure parametersUpdated: Feb 2026
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- 100000
- 100000

Estimated 1 Rep Max

0

90% (Heavy Training)

0

80% (Hypertrophy)

0
Assumptions used
These are the live inputs behind the result. Change one at a time before acting on the estimate.

Weight Lifted (lbs)

135

Reps Performed

5

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Expert Analysis & Methodology

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.