Turn a completed set's weight, reps, and RPE into your estimated one-rep max for today.
| Target RPE | Weight (5 reps) |
|---|
RPE (Rate of Perceived Exertion) rates how hard a set felt on a scale of roughly 6 to 10. RIR (Reps in Reserve) is the same concept from the other direction — how many more reps you could have done. The two are directly linked: RPE 8 means 2 reps in reserve, RPE 9 means 1 rep in reserve, and RPE 10 means 0 reps in reserve, or absolute muscular failure.
Traditional percentage-based training locks your working weight to a fixed 1RM that doesn't account for daily fluctuations in fatigue, stress, nutrition, or sleep. RPE auto-regulates your training instead — matching the weight to what you're actually capable of that day. This reduces injury risk on bad days and can push slightly harder on good days, all while targeting the same intended training stimulus.
This tool uses the validated RTS (Reactive Training Systems) RPE chart — the same chart popularized by Mike Tuchscherer and widely used in powerlifting — rather than a generic formula. Your reps and RPE are matched to the chart's corresponding percentage of 1RM, then your lifted weight is divided by that percentage to estimate your e1RM for today. Because it's chart-based, this is more precise than linear formulas like Epley for the RPE 6-10 range, especially at low reps.
RPE rates effort (6-10 scale); RIR counts reps left in the tank. RPE 8 = 2 RIR, RPE 9 = 1 RIR, RPE 10 = 0 RIR.
RPE auto-regulates for daily fatigue, sleep, and stress, unlike a fixed 1RM percentage that ignores how you actually feel that day.
Match your reps and RPE to the RTS chart's percentage, then divide your lifted weight by that percentage.
They're most accurate for 1-8 reps. Above 10 reps, fatigue and burning sensations make true failure harder to judge.