One Rep Max Calculator
Estimate your one rep max from the weight you lifted and the number of reps completed.
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Result
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Formula
How it works: The calculator uses three common formulas and averages them to estimate your one rep max and training max.
Review and Methodology
This calculator runs locally in your browser. Inputs are converted into the units required by the formula, and the result is paired with supporting references so you can verify the method before using it for planning or estimates.
Worked Example
How One Rep Max Estimation Works
A one rep max is the maximum weight you can lift for a single repetition with proper form. Since testing a true max can be fatiguing and risky, many lifters estimate it from a challenging set of multiple reps.
- Lower rep sets usually produce more reliable one rep max estimates than very high rep sets
- The calculator compares several common strength formulas instead of relying on only one
- A training max is often set at about 90% of your estimated one rep max for safer programming
- Good form matters more than the estimate. Do not chase a number at the expense of technique
Use one rep max estimates to plan progressive overload, choose working weights, and track strength changes over time.
You can also calculate changes using our Protein Needs Calculator, Calorie Surplus Calculator, Macro Calculator or Water Intake Calculator.
Frequently Asked Questions
What is a one rep max?
A one rep max is the heaviest weight you can lift once with proper form for a given exercise such as bench press, squat, or deadlift.
Is this safer than testing a real max?
Usually yes. Estimating from a moderate rep set reduces fatigue and risk compared with attempting a true all-out max too often.
How accurate is a one rep max calculator?
It is an estimate, not a guarantee. Accuracy depends on exercise choice, lifting experience, fatigue, and how close the set was to true effort.
What is a training max?
A training max is a reduced planning number, often about 90% of your estimated one rep max. Many strength programs use it to keep workouts challenging but sustainable.
Is it possible to embed the One Rep Max Calculator on another website?
Yes, embedding the One Rep Max Calculator is free. Hit the "Embed" button on this page, adjust the width, height, and theme, then grab the iframe code. It works on WordPress, Wix, Squarespace, Shopify, and plain HTML pages. No registration needed. Full instructions at calculory.com/services/embed-calculators.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.
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