How this calculator works
A submaximal set can estimate the heaviest load you might lift once with similar technique. This is useful for programming percentages while avoiding frequent maximal attempts.
The calculator averages two common equations because no single equation is best for every lift or lifter. Lower-body compound lifts, upper-body lifts and isolation exercises can behave differently.
The result averages Epley (weight × [1 + reps/30]) and Brzycki (weight × 36/[37 − reps]). Both become less reliable as repetitions rise.
How to use the result
Use a technically consistent set taken close to—though not necessarily all the way to—failure. If five repetitions were easy, the calculator will underestimate capacity.
Round the result to a load your equipment allows and treat it as a programming reference. A predicted 100 kg does not obligate you to test 100 kg.
Get a more reliable result
Use a recent, technically sound set taken close to failure with the same exercise variation you want to estimate. Sets of roughly 2–10 repetitions are usually more useful than very high-repetition work. Enter only the external load shown by the equipment and keep units consistent.
Common errors that change the answer
- Using a set stopped many repetitions before failure, which tends to underestimate capacity.
- Estimating from 15–20 repetitions, where endurance and equation error grow.
- Comparing results across different range of motion, machines, bar paths or technique.
What to do next
- Use 2–10 clean repetitions; estimates from very high reps are noisier.
- Recalculate from the same exercise and technique.
- Use a spotter or safety arms for heavy barbell work.
Guides that support this calculator
Frequently asked questions
Which formula is most accurate?
Accuracy depends on lift, repetition range and training history. Averaging common equations reduces dependence on one model but does not remove error.
Should beginners test 1RM?
They rarely need to. A controlled multi-rep estimate is usually safer and more repeatable while technique develops.
How often should I recalculate?
Every four to eight weeks, or after a clear performance change, is usually enough for programming.