What RPE means
RPE — Rate of Perceived Exertion — is how hard a set felt, scored from 1 to 10. In strength training it's really a measure of reps left in the tank: RPE 10 is a true max with nothing left, and every half-point below that is roughly one more rep you could have done. Its mirror is RIR (reps in reserve):
- RPE 10 — 0 reps in reserve, an all-out grind
- RPE 9 — 1 rep left
- RPE 8 — 2 reps left
- RPE 7 — 3 reps left, still moving fast
How the conversion works
Every reps-and-RPE pair maps to a percentage of your one-rep max. A set of 5 reps at RPE 8, for instance, sits at about 81% of your 1RM. From there the maths runs both ways: divide a weight by that percentage to estimate your max, or multiply your max by it to get the weight to load. This calculator does whichever direction you pick with the toggle, and rounds the loading mode to real plates.
About the chart
These numbers are the widely used Tuchscherer RPE chart, popularised through Reactive Training Systems. It's a strong estimate, not a law — your real percentages shift with the lift, your training history and how the day is going. Use it to autoregulate sensibly, and trust a recent tested set over the chart when the two disagree.