One Rep Max Calculator
Estimate your one-rep max from weight and reps performed.
Last updated: June 13, 2026
Calculator
Results
How to Use This Calculator
- 1Enter the weight you lifted.
- 2Enter the number of reps completed.
- 3View estimated 1RM and training percentages.
Formula Explanation
The Epley formula estimates the maximum weight you could lift for a single repetition based on a sub-maximal lift.
Variables:
Worked Examples
185 lbs for 5 reps
- 1. 1RM = 185 × (1 + 5/30)
- 2. = 185 × 1.167 = 215.8
Why Use This Calculator
- Estimate max without testing it.
- Plan training loads by percentage.
- Track strength progress.
- Set realistic training goals.
Tips & Best Practices
- The estimate is most accurate with 3-10 reps. Higher reps decrease accuracy.
- Test your actual 1RM only occasionally — it is taxing on the body.
- Warm up thoroughly before heavy lifting.
- Training at 70-85% of 1RM is optimal for building strength.
Common Mistakes to Avoid
❌ Using too many reps for the estimate.
✅ For best accuracy, use a weight you can lift for 3-10 reps. Sets of 15+ reps produce less reliable estimates.
❌ Training at your 1RM regularly.
✅ Max lifts are taxing and risky. Use 1RM estimates for programming — train at 70-85% for strength gains.
Frequently Asked Questions
What formula does this use?
How often should I test my 1RM?
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<iframe src="https://redicalc.com/embed/fitness/one-rep-max-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="One Rep Max Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.
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