Free Tools
RPE Calculator
Rate a working set by its reps and RPE, and we'll estimate your 1-rep max — then tell you exactly what to load for any reps at any RPE next time.
RPE (Rate of Perceived Exertion) turns "how hard did that feel" into a number you can program with. It uses the standard reps-in-reserve chart, so you train to the right effort instead of a fixed percentage that ignores how you feel on the day.
1. Rate the set you did
RPE 8 — 2 reps left in the tank.
Enter the weight, reps and RPE of a working set — we'll estimate your 1-rep max and tell you exactly what to load for your next set.
RPE / RIR chart
Strength tool
One-Rep Max Calculator
Estimate your 1RM from an all-out set, then get your working loads at every percentage.
Strength tool
Barbell Plate Calculator
Enter the weight your RPE work calls for — see the exact plates to load on each side.
Why train with RPE
Fixed percentages assume every day is the same. RPE does not. Rating a set on the 1 to 10 scale lets you push when you feel strong and back off when you do not, while still hitting the intended effort. Over a training block that auto-regulation keeps hard sets hard and easy sets easy — the single biggest driver of progress after showing up consistently.
RPE and reps in reserve
The simplest way to rate a set is to ask how many more reps you could have done. That is your reps in reserve, and RPE is just ten minus it: two reps left is an RPE 8, one left is an RPE 9, nothing left is an RPE 10. This tool works in both, because a set of five at RPE 8 is the same effort as a seven-rep max — which is exactly how it converts to a percentage of your one-rep max.
Get honest with your rating
An RPE estimate is only as good as your RPE call. Most lifters, especially early on, under-rate hard sets and call a true RPE 9 a 7, which flatters the numbers. Film a set now and then and count the grind: if the bar slowed to a crawl, that was not an RPE 7. Treat the estimated max here as a training guide for load selection, not a competition number.
Common questions
What is RPE in weightlifting?+
RPE stands for Rate of Perceived Exertion, a 1 to 10 scale for how hard a set felt. In lifting it maps to reps in reserve: RPE 10 means you had nothing left, RPE 9 means one more rep was possible, RPE 8 means two, and so on. It lets you auto-regulate — training to a target effort rather than a fixed percentage that ignores how you feel that day.
How does RPE convert to a percentage of 1RM?+
A set of a given reps at a given RPE equals an all-out set of a few more reps, because reps in reserve = 10 minus RPE. For example 5 reps at RPE 8 (two in reserve) is about a 7-rep max, which sits near 81% of your 1RM. This calculator uses the standard Reactive Training Systems chart to do that conversion both ways.
What is the difference between RPE and RIR?+
They are two sides of the same coin. RIR (reps in reserve) counts the reps you could still have done: RPE 10 is 0 RIR, RPE 9 is 1 RIR, RPE 8 is 2 RIR. Many lifters find RIR easier to judge in the moment, then read it as an RPE. This tool shows both so you can use whichever you prefer.
How accurate is an RPE-based 1RM estimate?+
It is an estimate, and it is only as accurate as your RPE call. Rating is a skill: newer lifters tend to under-rate hard sets (calling a true RPE 9 an RPE 7), which inflates the number. Use it as a training guide for load selection, not a competition max, and it becomes more reliable as you get honest about how close to failure you really are.
Which supplements actually help me train harder?+
For strength and hard sets, creatine monohydrate at 3 to 5 grams a day is the most evidence-backed supplement there is, and a caffeinated pre-workout can lift a heavy session. Neither replaces good sleep, enough protein and sensible RPE management. This tool is a training aid, not medical advice.
Training near your limit?
Hard RPE work is where creatine and a solid pre-workout earn their place — the two supplements with real evidence behind them. Every product we track is scored 0–100 on how closely its doses match that evidence.
Informational only — not medical or coaching advice. RPE-to-percentage figures follow the standard reps-in-reserve chart and are estimates. Buy links are affiliate links; we may earn a commission at no extra cost to you.