RPE and RIR: how to rate effort in lifting

Lifting programs used to set every weight as a percentage of your one-rep max. The trouble is that strength moves from day to day. After a bad night, 80% of your max can feel like 90%. RPE handles that by fixing the effort instead of the weight. You pick whatever load produces the effort the plan asks for.

Where the scale comes from

The original rating of perceived exertion is the Borg scale, created by Swedish psychologist Gunnar Borg and still used for cardio and exercise testing. It runs from 6 to 20. Lifting borrowed the idea and tied it to something you can count. Powerlifting coach Mike Tuchscherer popularized a 1–10 version based on reps left in the tank, and a 2016 study led by Michael Zourdos tested it as a reps-in-reserve scale for resistance training.

RIR is the plain way to think about it. RPE just turns it into a scale where higher means harder. Most programs that use RPE keep working sets between 6 and 9. Sets at RPE 7 or above, three reps or fewer from failure, are what coaches usually mean by hard sets when they count training volume.

A worked example

Your plan says 3 sets of 5 squats at RPE 8. You warm up and load 100 kg. The first set moves well, and you’re confident you had two more reps. That’s RPE 8, so you stay at 100 kg. On the second set, rep five slows down and only one more was possible. That’s RPE 9, so you drop to 95 kg for the last set and keep the effort where the plan wants it.

RPE also lets you estimate strength without testing a max. Five reps with two in reserve means 100 kg is roughly your seven-rep max. Put 100 kg and 7 reps into a one-rep max calculator and the Epley formula gives about 123 kg. It’s an estimate, but it’s close enough to set percentages for the next few weeks.

Why beginners misjudge it

Rating effort is a skill. New lifters usually underestimate how many reps they have left. A set that feels like the limit is often several reps short of real failure, because the burn and the slowing bar are unfamiliar. Research on reps-in-reserve ratings finds they get more accurate as a set gets closer to failure, and on heavier sets with fewer reps. High-rep sets are hard to judge for everyone, because discomfort builds long before the muscle actually fails.

That’s why many coaches start beginners on plain rep targets and add RPE later. To calibrate, take the last set of a safe exercise to failure now and then, and compare the real count with your guess. Use a machine or dumbbells for this, not a heavy barbell squat without safety bars.

What changes your RPE on a given day

• Sleep: A short night can make a familiar weight feel noticeably heavier.
• Food and caffeine: Training on an empty stomach, or after a big coffee, changes how hard a set feels.
• Accumulated fatigue: Late in a hard week, or late in a session, the same load rates higher.
• Rest between sets: Short rest raises the effort of the next set.
• The exercise: Effort is easier to read on a bench press than on a 20-rep set of leg presses.

Common mistakes

• Rating the whole session: RPE belongs to one set, rated right after you put the weight down.
• Rating by the burn: A burning muscle isn’t the same as being close to failure. Ask how many clean reps were left.
• Grinding every set at RPE 10: Sets to failure cost more recovery. Most work can stop one to three reps short.
• Ignoring the number: If the plan says RPE 8 and the set was a 9.5, the next set needs less weight.

How FORM uses it

FORM’s workout tracker logs the weight and reps of every set and suggests a heavier load after three sessions at the same weight. RPE is how you judge whether that jump is right on the day. If your last set already felt like RPE 9.5 or 10, keep the weight and build reps first. Progressive overload explains how reps and load fit together.

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