1RM Estimation Calculator

How 1RM Estimation Works

Direct one-rep max testing — loading a bar to the absolute limit of your strength — carries real injury risk and requires significant recovery time. Submaximal estimation offers a safer alternative: you perform a set with a manageable weight for multiple reps, then use predictive equations to extrapolate your maximum.

Each formula in this calculator was developed from different populations and methodologies, which is why they can produce different results. Averaging across all seven smooths out the individual biases of any single model and consistently outperforms any one formula in isolation — a well-established finding in sports science literature.

For best accuracy, use a weight you can perform 3–8 reps with near-maximal effort. Above 10 reps, fatigue and technique breakdown introduce too much variability for reliable estimation. Below 3 reps, small measurement errors have an outsized effect on the result.