STARK / Tools
RPE calculator: your load for any reps and RPE
Enter a recent set: the weight, the reps and how hard it felt. You get your estimated 1RM and the load to use for your next set at the reps and RPE of your choice.
Calculate your load by RPE
1. Your recent set
Estimated 1RM
– kg
2. Your next set
Load to use
– kg
Your loads by reps and RPE
| Reps | RPE 10 | RPE 9 | RPE 8 | RPE 7 |
|---|
Short answer: a set of 5 reps at RPE 8 (2 reps in reserve) is about 81 % of your 1RM. If you did 100 kg × 5 at RPE 8, your estimated 1RM is about 123 kg, and 8 reps at RPE 8 would be about 91 kg.
RPE and RIR: the scale
RIR is the number of clean reps you could still have done at the end of the set. RPE is 10 minus that number. Use the one that feels most natural; they are interchangeable.
| RPE | RIR | What it feels like |
|---|---|---|
| 10 | 0 | Maximal effort, no more reps possible |
| 9.5 | 0 | No more reps, but slightly more weight was possible |
| 9 | 1 | One more rep, surely |
| 8.5 | 1–2 | One more for sure, maybe two |
| 8 | 2 | Two more reps possible |
| 7 | 3 | Three more reps possible, the bar still moves fast |
| 6 and below | 4+ | Warm-up or technique work |
The RPE chart: % of 1RM by reps and RPE
The calculator uses the RPE chart popularised by powerlifting coach Mike Tuchscherer. It is based on one idea: a set of 5 at RPE 8 is as heavy as a set of 7 to failure, because in both cases you could have done 7 reps. Each cell gives the percentage of your 1RM.
| Reps | RPE 10 | RPE 9 | RPE 8 | RPE 7 |
|---|---|---|---|---|
| 1 | 100 % | 96 % | 92 % | 89 % |
| 2 | 96 % | 92 % | 89 % | 86 % |
| 3 | 92 % | 89 % | 86 % | 84 % |
| 4 | 89 % | 86 % | 84 % | 81 % |
| 5 | 86 % | 84 % | 81 % | 79 % |
| 6 | 84 % | 81 % | 79 % | 76 % |
| 7 | 81 % | 79 % | 76 % | 74 % |
| 8 | 79 % | 76 % | 74 % | 71 % |
| 9 | 76 % | 74 % | 71 % | 68 % |
| 10 | 74 % | 71 % | 68 % | 65 % |
| 11 | 71 % | 68 % | 65 % | 63 % |
| 12 | 68 % | 65 % | 63 % | 60 % |
How reliable is it?
- The chart is an average. Some people do more reps at a given percentage, others fewer: use the result as a starting load.
- It is built around compound barbell lifts. On machines and isolation exercises, rely more on your own RPE than on the percentage.
- Rating RPE takes practice. Beginners tend to underestimate the reps they have left, especially on long sets.
- The calculator stops at 12 reps and RPE 6.5: beyond that, the estimate is too rough to be useful.
To learn more about rating your sets, read the RPE and RIR guide.
Your last session, next to the set you are logging
STARK shows what you lifted last time on every exercise, estimates your 1RM from each set and tells you when to add weight. Free on iPhone, with Apple Watch.
Frequently asked questions
What is RPE in strength training?
RPE (rating of perceived exertion) rates how hard a set was on a scale of 10. In strength training, it is tied to the reps you had left: RPE 10 means none, RPE 9 one, RPE 8 two.
What is the difference between RPE and RIR?
They describe the same thing from two sides. RIR counts the reps left in reserve; RPE is 10 minus that number. A set with 2 RIR is a set at RPE 8.
Which RPE should I train at to build muscle?
Most working sets for muscle growth land between RPE 7 and 9, that is one to three reps in reserve. Going to RPE 10 on every set adds fatigue without a clear extra benefit for most people.
Is the RPE chart accurate for everyone?
No. The chart is an average built mainly around compound barbell lifts. Some people do more reps at a given percentage, others fewer. Use the result as a starting load and adjust it with your own RPE during the session.
How do I log RPE?
Write it next to the weight and reps, for example 100 × 5 @8. In STARK, you log the weight and reps of every set and compare them with your last session.