RPE calculator
Enter the set you did and how hard it felt. This is the lifting RPE scale, not the Borg scale.
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Working weights
What does RPE mean in lifting?
Rate of perceived exertion on a 6 to 10 scale, where 10 means no reps left in the tank and 8 means you could have done two more. Reps in reserve is simply 10 minus the RPE. Combined with a rep count it maps to a percentage of your one-rep max.
Two different RPE scales exist
This causes real confusion. The lifting RPE scale runs 6 to 10 and describes reps left in reserve. The Borg scale, used in cardiovascular testing, runs 6 to 20 and maps loosely to heart rate.
An RPE of 8 means something quite specific in a squat rack — two reps left — and something completely different on a treadmill protocol. This calculator uses the lifting scale.
The lifting scale is sometimes written as RIR instead, for reps in reserve, which inverts it: RPE 8 is RIR 2. Both describe the same thing.
Why lift by RPE rather than percentage
Percentage-based programming assumes your one-rep max is a fixed number. It is not — it moves with sleep, stress, nutrition and where you are in a training block.
RPE lets the load float with the day. Prescribing three sets of five at RPE 8 asks for the same relative effort every session, where prescribing 80% asks for the same absolute load regardless of how you turned up.
The trade-off is that RPE takes practice to judge accurately, and most lifters underestimate it at first — calling an RPE 9 set an RPE 7 is extremely common in the first few months.
How the estimate works
A chart lookup, not an equation.
reps in reserve = 10 − RPEthe chart maps (reps, RPE) to a percentage of 1RM:1 rep @ RPE 10 = 100%5 reps @ RPE 8 = 81.1%8 reps @ RPE 8 = 73.9%estimated 1RM = weight × 100 ÷ percentage
The estimate degrades as reps climb. A triple at RPE 9 predicts a one-rep max reasonably well; a set of twelve predicts it poorly, because endurance and pain tolerance start to matter more than maximal strength.
It also varies by lift. Most lifters can hold a higher percentage for more reps in a squat or deadlift than in a bench press, so a single chart across all lifts is an approximation by design.
Worked example: 100 kg for 5 at RPE 8
You squat 100 kg for five reps and judge it at RPE 8, meaning two reps left in reserve.
- Set performed100 kg × 5 @ RPE 8
- Chart percentage81.1%
- 100 ÷ 0.811123.3 kg
- Working set at 80%98.6 kg
- Working set at 70%86.3 kg
An estimated one-rep max of about 123 kg.
If that set was really an RPE 9, the estimate drops to about 119 kg. A single point of RPE misjudgement moves the estimate by roughly 3% to 4%, which is why honest self-assessment matters more than chart precision.
Using RPE well
- Judge the RPE immediately after the set, before the memory softens
- Ask how many more reps you could have completed, not how hard it felt
- Expect to underestimate at first — most lifters do for several months
- Video helps: bar speed on the last rep is a good reality check
- Do not chase RPE 10 regularly; it is expensive to recover from
- The estimate is a planning tool, not a number to test against
Common questions
What does RPE 8 mean?
You could have completed two more reps with good form. The lifting RPE scale describes reps in reserve, so RPE 10 is nothing left, RPE 9 is one more, and RPE 8 is two more.
Is RPE the same as the Borg scale?
No. The Borg scale runs 6 to 20 and is used in cardiovascular testing. The lifting RPE scale runs 6 to 10 and describes reps left in reserve. They share a name and nothing else.
How accurate is an RPE-based 1RM estimate?
Reasonable at low rep counts and poor at high ones. A triple at RPE 9 predicts well; a set of twelve does not, because endurance rather than maximal strength starts to govern the outcome. Treat it as a planning figure, not a tested max.
What is RIR?
Reps in reserve — the same idea inverted. RIR 2 is RPE 8, RIR 0 is RPE 10. Some programmes prescribe one and some the other, but they describe identical effort.
Should I use RPE or percentages?
RPE adapts to how you turn up on the day, which percentages cannot. Percentages are easier to plan and audit. Many programmes use percentages for the block structure and RPE caps to stop a bad day turning into a bad week.
Where these numbers come from
- National Strength and Conditioning Association — Rating of perceived exertion Background on perceived exertion scales in resistance training.
Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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