Give it your max, the reps you're planning, and either an RPE or the reps you mean to leave behind. It returns the load.
Estimates are for general guidance only and are not medical advice. For a personalised plan, book a free guided tour at RPM Gym.
The headline is a weight: what to put on the bar for the reps and the effort you asked for. Under it sit the percentage of your 1RM that load represents, the same effort written on the other scale, and the set the tool treated yours as.
That last line is the method, and it deserves a read rather than a glance. Five reps at RPE 8 is handled as a set of seven taken to failure, because RPE 8 means two reps left. The percentage then comes from running the rep-max model backwards on those seven reps — the same mean of Epley and Brzycki the 1RM calculators here run forwards. No grid sits behind this page.
Using that same model in both directions is the point, not a detail. A max estimated on one page and spent on another has to survive the trip: 100 kg for five estimates a 114.6 kg max, and asking this page for a five-rep load at RPE 10 hands back 100 kg. It used to hand back 98.2, because this page inverted only half the model the estimate was built from.
The RPE percentage charts in circulation would have been easier. They are also untraceable: they pass from programme to programme without a published derivation, and a table of unattributed percentages reads as more authoritative than the equations it displaced. Epley and Brzycki are named, dated equations with stated forms and known weaknesses, and those weaknesses can be printed on the page. That trade is worth making even though the output looks less tidy.
One case is fixed rather than modelled. A single at RPE 10 is 100% of your 1RM by definition, and that is what comes back — anything less would be the tool telling you your max is not your max.
Reps in reserve = 10 − RPE (RPE 10 = 0 RIR, RPE 9 = 1, RPE 8 = 2, and so on) Effective reps = reps you plan + reps in reserve Epley load = 1RM ÷ (1 + effective reps ÷ 30) Brzycki load = 1RM × (37 − effective reps) ÷ 36 Load = the mean of those two, fixed at the 1RM itself for one effective rep % of 1RM = load ÷ 1RM
A 140 kg squat max, five reps planned, RPE 8.
115.1 kg for five at RPE 8; 118.6 kg for five at RPE 9. A whole point of RPE is worth about 3.5 kg here, or 2.5% of the max — roughly the size of the error a pooled analysis found in lifters' own predictions of the reps they had left. Load the number, then let the set correct it.
How close a set came to failure, counted in reps rather than in feeling. RPE 10 means the next rep was not there. RPE 8 means about two more were. The resistance-training version of the scale is anchored to reps in reserve for exactly that reason: hard is not a number, but two left is.
The same information counted from opposite ends. RIR counts up from zero, RPE counts down from ten, and 10 minus your RPE is your RIR. That is why there is no separate reps-in-reserve tool to build — enter either one here and the other is printed next to your load.
Because nobody can show where the numbers in one came from. Those charts are practitioner tables that got copied between programmes, and the version you find depends on who you asked. An equation with a citation behind it can be checked, argued with and corrected. A chart with no author cannot, and it would sit on this page looking more precise than the thing it replaced.
No, and the tool has no way to warn you. It returns the load your max implies for that effort, which is a fixed number until the max changes. What RPE 8 actually weighs on a given day moves with sleep, food, stress and what you trained two days earlier. Set the bar from the output and let the first working set adjust it.
Whole points only, because the reps-in-reserve anchor the tool converts through is a whole rep. Half a point sits between one rep left and two, and on five reps it comes to roughly 1.8 kg on a 140 kg max — under the smallest jump most gyms can load. Write halves in your log if they help you think; the arithmetic will not honour them.
The validation work points that way: experienced squatters rated a maximal single more accurately than novices, and the link between their ratings and bar speed was tighter. The practical version is to occasionally finish a set you would have called done and count what you were wrong by. Most people find the gap narrows once they have measured it a few times.
A percentage fixes the load and lets effort float; an RPE fixes the effort and lets the load float. This page is the bridge, printing one beside the other so a programme written in either can be run in either. As a rule of thumb, percentages are easier to plan in advance and RPE is easier to execute on a day that did not go to plan.
Two candidates, and they are distinguishable. If it feels light at every rep count you try, the 1RM you entered is low — re-estimate it from a recent set. If it feels light at five and brutal at twelve, that is your own rep-strength profile rather than a fault in the equation, and the fix is a personal offset at the high-rep end rather than more decimal places.
Sleep, the week behind you and the way the first warm-up moves all shift where that effort lands, and adjusting the bar mid-session is a judgement worth borrowing before you own it. Book a free guided tour at RPM Gym in Al Manhal.