How We Estimate Your Bench Press 1RM
The Bench Press 1RM Calculator uses the Mayhew equation as its default estimate. Unlike many general-purpose 1RM formulas, the Mayhew equation was developed from research specifically examining the relationship between repetition performance and one-repetition maximum in the bench press.
That makes it a useful starting point for estimating bench press strength from a submaximal set.
No prediction equation perfectly describes every lifter. Bench press repetition strength can vary with training history, technique, pause length, grip width, and individual muscular endurance. For that reason, the calculator also allows you to compare your result with other commonly used 1RM equations.
Why Might I Choose a Different Bench Press Formula?
Epley may be useful if you prefer a simple general-purpose equation or already use Epley estimates throughout your training log.
Brzycki generally produces a relatively conservative estimate at common lower rep ranges and can be useful if you prefer not to base training percentages on the higher end of the predicted range.
Lander provides another established estimate and is useful as a comparison when you want to see how sensitive your predicted max is to the equation being used.
If several formulas produce nearly the same result, you can have greater confidence that the input set provides a stable estimate. If the formulas disagree substantially, consider testing with a heavier weight for fewer repetitions. Switching formulas does not automatically make an estimate more accurate.
Which 1RM Formula Is Best for Me?
The best equation for an individual lifter is the one that most consistently reflects their actual performance.
If you know both a recent true 1RM and a recent repetition-max set, compare each formula against that result. For example, if your actual squat max is 405 lb and Lander repeatedly predicts about 400–410 lb while Epley predicts 425 lb, Lander may be the more useful formula for your squat.
This does not necessarily mean that equation is more accurate for your bench press or deadlift. Your repetition strength can differ between movements.
Rep Range and Consistent Tracking
For the most useful estimate, use a challenging set of approximately 2 to 8 repetitions. As rep counts increase, differences in muscular endurance become more important and the predictions from different formulas tend to spread farther apart.
Formula selection matters less when reps are low because common equations tend to produce more similar estimates near the low-repetition end.
When using estimated 1RM to track progress, consistency is often more important than chasing the formula that produces the highest or lowest number. Compare sets performed with similar technique and rep ranges using the same equation.
Research comparing 1RM prediction equations suggests accuracy can vary by exercise, rep range, and population. Your own repetition strength may fit another equation more closely.
Method and Limitations
All formulas use completed reps plus entered RIR as estimated repetition capacity. Technique differences, fatigue, exercise selection, and individual repetition endurance can affect the result. The formula range is a comparison, not a statistical confidence interval.
These estimates are educational, not medical advice or a substitute for direct testing by a qualified professional. Prediction error and individual variation are expected.