RPE
calculator

Give a set you actually did — the weight, the reps, and how many you had left before failure — and read off the percentage of your one-rep max it represented, the max it implies, and what to load next at any RPE. Pounds or kilos.

RPE, on the lifting scale, is reps in reserve: an RPE 10 set is taken to failure, an RPE 8 set leaves two reps in the tank, an RPE 6 leaves four. Give this calculator the weight, the reps, and the RPE, and it returns the percentage of your one-rep max that set represented and the 1RM it implies — because the load depends only on how many reps you would have reached at failure, which is the reps you did plus the reps you left. It runs on the Tuchscherer / Reactive Training Systems chart, validated as a reps-in-reserve scale by Zourdos et al. (2016).

How the math works

Two steps, one lookup. First, RPE converts to reps in reserve: RPE = 10 − RIR, so RPE 8 means two reps left. Add those to the reps you performed to get your reps-to-failure, and that single number maps to a percentage of 1RM on the RTS chart — 5 reps-to-failure is 86.3%, whether that was 5 reps at RPE 10 or 3 reps at RPE 8. Divide the weight by that percentage to back out the estimated max. The reps-in-reserve definition of RPE was validated by Zourdos et al. (2016); the percentage chart itself comes from Tuchscherer's Reactive Training Systems manual (2008).

Half-RPE steps fall between the rows: an RPE 8.5 triple is 4.5 reps-to-failure, halfway between the 4-rep and 5-rep anchors. The chart is unit-agnostic — it scales straight with the load — so an estimate in pounds converts to kilograms by the exact factor 1 lb = 0.45359237 kg, and the unit toggle above only touches the weight field.

Worked example

A lifter squats 315 lb (143 kg) for 3 reps and rates it RPE 8 — two reps in reserve.

• Reps to failure: 3 performed + 2 in reserve = 5
• %1RM at 5 reps to failure: 86.3%
• Estimated 1RM: 315 ÷ 0.863 = 365 lb (166 kg)

Now use it forward. To program 5 reps at RPE 8, that set is 7 reps-to-failure, or 81.1%: 365 × 0.811 = 296 lb (134 kg). You can't load 296, so you build the nearest bar — 295 lb on a 45 lb bar, or 132.5 kg on a 20 kg bar — and accept that rounding down nudges the real effort a touch below RPE 8. That last step is where a plate calculator earns its place next to this one.

The RPE chart

The reference grid: percentage of 1RM for each rep count and RPE. Multiply the cell by your own max to get a working weight. Blank cells fall past the 12-rep edge of the chart, where an RPE call that far from failure stops meaning much.

Every cell on one reps-to-failure diagonal is the same percentage — RPE 10 for 5 reps, RPE 9 for 4, and RPE 8 for 3 all read 86.3%, because they are all five-reps-from-failure efforts.

When this calculator is wrong

The estimated 1RM this tool backs out is a rep-based estimate, and those hold up only in a narrow window. Across the five common 1RM formulas and against measured maxes, estimates are reliable up to about 6 reps, marginal from 7 to 10, and past 10 reps they measure muscular endurance more than maximal strength (opinions.md O4, grounded in LeSuer et al. 1997). A set at RPE 8 for 3 reps sits comfortably inside that window; a set at RPE 6 for 10 reps does not, which is why the chart simply runs out. The counter-case is the good news: for the submaximal, RPE-based work this calculator is built to program — sets in the 70–85% range judged by effort rather than by a fixed number on the bar — even a noisy 1RM estimate is fine, because the set is autoregulated to how it feels on the day. The error only bites when you feed a soft estimate into heavy percentage work at 85% and above.

Three more limits worth naming:

• The RPE call is the real error source, and it's biased. Zourdos et al. (2016) found less-experienced and less-strong lifters estimate their reps in reserve less accurately than stronger, seasoned lifters, and everyone reads it better close to failure than far from it. A set you log as RPE 8 that was really RPE 9.5 shifts the implied load by roughly 2–3 percentage points of 1RM per rep — enough to matter. New lifters tend to under-rate: what feels like "two left" is often the last rep they had.
• The output isn't a weight you can load. 81.1% of a 365 lb max is 296 lb, and no bar builds that exactly. Round to the nearest 5 lb or 2.5 kg and the true RPE drifts slightly from the target; the plate calculator shows what you can actually build.
• The chart is one curve for every lift. Most lifters can grind more reps at a given percentage on a deadlift than on a bench, so a single reps-to-failure chart is an average across movements. Treat it as a starting map and let a couple of weeks of your own RPE-tagged sets calibrate it per lift.

What to do with the result

Use the percentage, not just the estimated max. Once you know a set was, say, 81%, you can hold that intensity or step it by reading the chart forward: the same weight for more reps raises the RPE, a lighter weight for the same reps lowers it. Set your next session's loads from the target strip above, then round each to a loadable bar with the plate calculator or pull the whole percentage ladder off an estimated max with the percentage calculator.

Calibrate the RPE itself, because that's the input the whole estimate leans on. Every few weeks, take one set closer to failure than you normally would and count the reps you actually had left against the reps you called — if the gap is consistent, adjust your ratings. Track your top sets with their RPE for two or three weeks before trusting the implied max; a single set on a bad day tells you less than a short run of them.

Common questions

What is RPE in weightlifting?

Rate of Perceived Exertion — on the resistance-training scale, how many reps you had left before failure. RPE 10 is a set you couldn't have added a rep to; RPE 9 is one rep short of that; RPE 8 is two short, and so on. It's a way to prescribe effort instead of a fixed weight, so the load self-adjusts to how strong you are on the day.

How do you convert RPE to a percentage of 1RM?

Turn the RPE into reps in reserve (RIR = 10 − RPE), add them to the reps you did to get your reps-to-failure, and look that up on the RTS chart. Three reps at RPE 8 is five reps-to-failure, which is 86.3% of 1RM. Both the RPE and the rep count are needed — RPE alone doesn't fix a percentage.

Is RPE 8 the same as 80% of 1RM?

No — it depends on the reps. RPE 8 for 1 rep is about 92%; RPE 8 for 5 reps is about 81%; RPE 8 for 8 reps is under 74%. The percentage falls as the reps rise, because more reps at the same "two in reserve" means a lighter bar. That's the whole reason this calculator asks for reps as well as RPE.

What's the difference between RPE and RIR?

They're two sides of one number: RPE = 10 − RIR. Reps in reserve counts up from failure (0 left is hardest); RPE counts down to it (10 is hardest). Some programs are written in RIR, some in RPE; "3 reps at RPE 8" and "3 reps with 2 in reserve" are the same prescription.

How accurate is the RPE chart for beginners?

The chart is only as accurate as the RPE call feeding it, and that call is the weak point for newer lifters. Research on the reps-in-reserve scale (Zourdos 2016) found less-experienced and weaker lifters judge proximity to failure less reliably, and most under-rate — they call a set RPE 8 when they had maybe half a rep left. Taking occasional sets close to failure and counting the reps you truly had in reserve is how you tighten it.

Can I find my 1RM with RPE instead of testing it?

You can estimate it, and for programming that's usually enough. A set of 3–6 reps at RPE 8–9 gives a solid estimate; past 10 reps, or far below RPE 7, the number drifts. For a max you're going to attempt in competition or a true 1RM day, test it — an estimate is a planning tool, not a substitute for the attempt.