1 Rep Max Calculator

Calculate your estimated one-repetition maximum (1RM) for any exercise based on the weight you can lift for a given number of repetitions.

How to Use This Calculator

Enter the weight you lifted for a specific exercise
Input the number of repetitions you completed with that weight
Select your preferred weight unit (pounds or kilograms)
Choose a calculation formula (Epley is most commonly used)
Click Calculate to see your estimated 1RM and training weights

Formula Used

Epley Formula: 1RM = Weight × (1 + Reps/30)

Where:

1RM = Estimated one-repetition maximum
Weight = The weight lifted
Reps = Number of repetitions performed

Alternative Formulas:

Brzycki: 1RM = Weight × (36 / (37 - Reps))
Lander: 1RM = (100 × Weight) / (101.3 - 2.67123 × Reps)

Example Calculation

Real-World Scenario:

A lifter can bench press 185 lbs for 5 repetitions and wants to estimate their 1RM.

Given:

Weight = 185 lbs
Reps = 5
Formula = Epley

Calculation:

1RM = 185 × (1 + 5/30)

1RM = 185 × (1 + 0.167)

1RM = 185 × 1.167

Result: 215.9 lbs (estimated 1RM)

Why This Calculation Matters

Practical Applications

Designing effective training programs based on percentages of 1RM
Tracking strength progress over time
Setting appropriate training goals
Planning for competition attempts

Key Benefits

Reduces risk of injury from testing actual 1RM
Provides baseline for training intensity
Helps periodize training cycles
Enables comparison of relative strength

Common Mistakes & Tips

The formulas become less accurate when using more than 10 repetitions. For best results, use a weight you can lift for 1-10 reps with good form. The most accurate estimates typically come from 3-5 rep maxes.

The calculator assumes you're using a weight you could lift with proper form while relatively fresh. If you performed the set at the end of a long workout or while fatigued, your 1RM will be underestimated. Try to use weights from fresh sets when possible.

Your 1RM is specific to each exercise. A bench press 1RM won't translate directly to a squat or deadlift 1RM. Calculate your 1RM separately for each major lift you want to track.

Frequently Asked Questions

1RM estimations are generally most accurate when based on weights you can lift for 3-5 repetitions. They can be off by about 5-10% compared to actual 1RM testing. The accuracy also depends on your training experience and how close to failure your set was.

Testing actual 1RM carries higher risk of injury and requires significant recovery time. For most recreational lifters, estimation is safer and sufficient for training purposes. Competitive powerlifters may need to test actual 1RM closer to competitions.

Recalculate your 1RM every 4-8 weeks or whenever you notice significant strength gains. More frequent calculations aren't necessary as strength doesn't typically change dramatically in shorter periods. Track your progress over time to see long-term trends.

References & Disclaimer

Fitness Disclaimer

This calculator provides estimates only and should not replace professional fitness advice. Always consult with a qualified fitness professional before beginning or modifying any exercise program. Results may vary based on individual factors.

References

LeSuer DA, McCormick JH, Mayhew JL, et al. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. - Journal of Strength and Conditioning Research
National Strength and Conditioning Association (NSCA) - 1RM Prediction Equations - Professional guidelines for strength assessment
Greg Nuckols (2018). How Accurate Are 1RM Prediction Equations? - Stronger by Science

Accuracy Notice

This calculator provides estimates based on established formulas, but individual results may vary. Factors such as training experience, muscle fiber composition, and fatigue can affect actual 1RM. Use these estimates as a guide for training, not as absolute values.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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health fitness-exercise-performance rep max fitness body weight

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