One-Rep Max Calculator
Estimate a 1RM bench press, squat or deadlift and percentage reference loads.
Estimate one-rep max
Estimated strength
Estimated one-rep max
Percentage reference loads
Formula estimates and percentages are planning references, not requirements to attempt a maximum lift.
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How to use the one-rep max calculator
Enter the weight lifted, choose pounds or kilograms, and enter the number of technically sound repetitions completed from 1 through 12. The calculator estimates a one-repetition maximum and displays percentage-based reference loads.
Use a recent challenging set performed with consistent range of motion. A set stopped well before fatigue will generally underestimate capacity, while a set completed with deteriorating technique may overstate a useful training maximum.
Formula and percentage table
For two through twelve repetitions, the estimate uses the Epley formula: lifted weight multiplied by one plus repetitions divided by 30. If one repetition is entered, the lifted weight is already the observed one-repetition result and is not adjusted.
The table multiplies the estimate by percentages from 50% through 100%. Values are rounded to one decimal place and are not automatically adjusted to the plates or increments available in a particular gym.
Safety and limitations
Any formula is only an estimate. Accuracy varies by exercise, individual endurance, training experience, technique, set effort, and repetition count. Estimates derived from fewer high-quality repetitions are often more useful than estimates from long sets.
Do not treat the result as a requirement to attempt a maximal lift. A true one-repetition attempt carries a real risk of injury: form tends to break down under a maximal load, and a failed rep under a loaded bar can cause serious harm. That is why supervision, a spotter or safety bars, progressive loading, and sound technique matter, and why an estimate is usually the better option. The 100% row is the estimate itself, not a weight you have been cleared to lift today.
Seek qualified coaching or medical advice when warranted by your experience or health.
Frequently asked questions
Which one-rep max formula is used?
For sets of two through twelve repetitions, this calculator uses the Epley estimate of weight multiplied by one plus repetitions divided by 30. A completed single repetition is returned unchanged.
Why are repetitions limited to 12?
One-rep-max estimates generally become less reliable as repetitions increase because fatigue, pacing, and muscular endurance have more influence.
Should I test my actual one-rep max?
Not necessarily. A submaximal estimate can help plan training without the fatigue and technique demands of a true maximum attempt.
Are the percentage loads exact prescriptions?
No. They are arithmetic percentages of the estimate. Exercise selection, experience, fatigue, equipment, technique, and the intended number of repetitions all affect an appropriate working load.