What a rep max chart is for
Most well-written programmes are prescribed as percentages: 5 sets of 3 at 80%, a top single at 90%, back-off sets at 70%. A rep max chart is the translation layer between that prescription and the bar. It answers two questions — what weight is 80% for me, andhow many reps should 80% be good for — from a single input.
The chart is generated by inverting a one rep max formula. If Epley says1RM = weight × (1 + reps / 30), then rearranging gives the weight you should manage for any rep count: weight = 1RM / (1 + reps / 30). Do that for 1 through 12 and you have your table. You can switch the formula above; the differences are small at low reps and grow steadily as the reps climb.
Reading the percentages
The percentage column is the useful half of the table, because it's what programmes are written in. Broadly:
- 90–100% — 1 to 3 reps. Maximal strength and peaking work.
- 80–90% — 3 to 6 reps. The main strength-building range for most lifters.
- 70–80% — 6 to 12 reps. Hypertrophy work, and the bulk of most volume.
- Below 70% — technique practice, speed work and back-off sets.
Those bands are a map, not a rule. Muscle grows across a wide range of intensities as long as the sets are taken close enough to failure, so the choice between 6 and 12 reps is mostly about what you can recover from and what your joints tolerate.
Where a rep max chart misleads
A chart assumes a fixed relationship between percentage and reps, and that relationship is personal. Two lifters with identical 1RMs can differ by three or four reps at 80%. It's also lift-specific: most people get more reps at a given percentage on bench than on squat, and fewer on deadlift than on either.
That's the argument for RPE-based training, which prescribes effort rather than a fixed percentage and self-corrects on days when you're under-slept or under-fed. In practice most lifters use both: percentages to plan the block, RPE to adjust the session.
Using the chart in a session
Find your working weight in the table, thenbuild the ramp up to it andcheck what plates it takes. If you don't yet have a max to build from, estimate one from a recent set — this tool can do it inline, but the dedicated page shows how much the six formulas disagree, which is worth seeing once.