RPE calculator.

RPE (Rate of Perceived Exertion) and RIR (Reps in Reserve) are two ways to describe the same thing. RPE 10 means you could not have done another rep (zero RIR). RPE 9 means one rep left in the tank (1 RIR). RPE 8 is 2 RIR, RPE 7 is 3 RIR, and so on. Some coaches use the terms interchangeably. The chart in this calculator uses the RPE scale popularized by Mike Tuchscherer's Reactive Training Systems. If your program prescribes RIR instead of RPE, just subtract: RIR 2 = RPE 8, RIR 3 = RPE 7.

Reasonably accurate at moderate RPE values (7.5-9), and less accurate at the extremes. The chart assumes your RPE call was honest and that you are reasonably experienced at assigning it. Two common accuracy killers: underestimating how close you were to failure (most lifters do this for at least their first year), and using RPE data from very high rep sets (10 or more reps), where conditioning factors start to cloud the picture. For programming purposes, a well-calibrated RPE 8 on a 5-rep set typically gives a 1RM estimate within 5-8% of your true max.

Start with your main lifts: squat, bench, deadlift, overhead press. These are the movements where RPE calibration matters most and where the chart is most reliable. Accessories are harder to rate because fatigue from earlier in the session clouds the signal. Once you've been using RPE on your main lifts for several months and have a feel for it, you can layer it onto accessories if you want, but it's not necessary. Many coaches use absolute rep targets on accessories and save RPE for the barbell movements.

Above 12 reps, the accuracy of RPE degrades enough that the chart becomes unreliable as a programming tool. The problem is that at higher rep counts, your cardiovascular system and local muscular endurance start contributing to failure before pure strength does. Two lifters with the same 1RM can get very different rep counts at the same weight depending on their conditioning. The RTS chart was built from data collected at lower rep ranges where strength is the primary limiter. If you're working in 12-plus rep ranges, percentage-based programming tends to be a better fit.

Most lifters need 6-12 months of consistent use before their RPE calls are reliable. The most common error in the first few months is calling sets RPE 8 that were really RPE 9 or 9.5. Call it the comfort-zone problem. One useful drill: after finishing a set, try to add one more rep in your head. If you're confident you could have done it, your actual RPE was probably at least half a point lower than you called. Filming your sets helps. A set that looks like a grinder on video, hips shooting up and bar slowing to almost nothing, is not RPE 8. It's 9 or 9.5.