One-rep max (1RM) calculator

One-rep max by the Epley formula is weight × (1 + reps / 30): 100 kg for 5 reps gives about 116.7 kg. Below are working weights for 1–12 reps at RPE 6–10 from the Helms table, rounded to 2.5 kg.

Weight lifted, kg

Reps completed

Your estimated 1RM

116.7 kg

How it adds up

100 × (1 + 5 / 30) = 116.7 kg

What to load to hit a rep target with a given margin. RPE 10 is failure, RPE 8 leaves two reps in reserve, RPE 6 leaves four. Your rep count is highlighted.

×1 100 105 107.5 112.5 117.5 kg
×2 97.5 100 105 107.5 112.5 kg
×3 95 97.5 100 105 107.5 kg
×4 92.5 95 97.5 100 105 kg
×5 90 92.5 95 97.5 100 kg
×6 85 90 92.5 95 97.5 kg
×7 82.5 85 90 92.5 95 kg
×8 80 82.5 85 90 92.5 kg
×9 77.5 80 82.5 85 90 kg
×10 75 77.5 80 82.5 85 kg
×11 75 75 77.5 80 82.5 kg
×12 72.5 75 75 77.5 80 kg

Full RPE 6–10 table

Reps	RPE 6	RPE 7	RPE 8	RPE 9	RPE 10
1	100	105	107.5	112.5	117.5
2	97.5	100	105	107.5	112.5
3	95	97.5	100	105	107.5
4	92.5	95	97.5	100	105
5	90	92.5	95	97.5	100
6	85	90	92.5	95	97.5
7	82.5	85	90	92.5	95
8	80	82.5	85	90	92.5
9	77.5	80	82.5	85	90
10	75	77.5	80	82.5	85
11	75	75	77.5	80	82.5
12	72.5	75	75	77.5	80

What RPE means

RPE rates how hard a set was on a scale to 10, tied to reps in reserve: RPE 10 means nothing left, RPE 9 means one more, RPE 8 means two. The reps-in-reserve scale was described by Helms and colleagues in 2016.

It adapts to the day: if you slept badly, the same RPE 8 means a lighter weight, and the session still lands at the right effort.

RPE 10 failure
RPE 9 1 in reserve
RPE 8 2 in reserve
RPE 7 3 in reserve
RPE 6 4 in reserve

How it's calculated

Max uses the Epley formula (1985): 1RM = weight × (1 + reps / 30). A single rep already is your max, so for one rep the formula returns the weight itself.
Working weight is 1RM × the share of max for those reps and RPE from the table by Helms and colleagues (2016), then rounded to the nearest 2.5 kg — the way plates add up on a bar. Reps are already built into the table, so there's no second discount.
The app does the same: when a set in your plan is prescribed by RPE, the weight comes from this table and your best set.

Worked example: 100 kg × 5

100 × (1 + 5 / 30) = 116.7 kg. So 5 reps with two in reserve (RPE 8) is 95 kg, 8 reps with the same margin is 85 kg, and a single to failure is 117.5 kg.

When the formula is off

More than 10–12 reps: Epley's straight line overestimates the max, so the calculator, like the app, uses at most 12 reps.
Sets not taken to failure: the formula assumes nothing was left. If you had 2–3 reps in the tank, your real max is higher.
Different exercises: squat, bench and deadlift estimates tend to be closer than isolation lifts and machines.
Even at best it's a guide with an error of a few percent — good enough to pick working weights, not a replacement for a real attempt.

Programs for this goal

Frequently asked questions

How do I estimate my one-rep max without testing it?

Do a set of 3–8 reps close to failure and plug weight and reps into the Epley formula: weight × (1 + reps / 30). For example, 80 kg for 6 reps gives 96 kg.

How accurate is the Epley formula?

Up to 10 reps the estimate is usually within a few percent of a real max. The longer the set, the bigger the error, which is why the calculator stops at 12 reps.

What weight should I use for 8 reps?

It depends on the margin. With a 100 kg 1RM, 8 reps with two in reserve (RPE 8) is about 75 kg, and to failure about 77.5 kg. For your own max, see row 8 of the table.

Do I need to test my max for real?

Not to pick working weights: the estimate is enough, and a max attempt is the heaviest, riskiest set you can do. If you test anyway, warm up and use a spotter.

This is an estimate for healthy adults, not medical advice. With an illness, pregnancy or medication, talk to your doctor.