One-Rep Max Calculator

Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. You don't have to actually attempt a maximal single to know it. Enter a weight you lifted and how many clean reps you got, and this calculator estimates your 1RM using six published formulas, then builds the numbers you actually train with: a percentage loading chart, a rep-max table, a warmup ramp, and barbell plate loading. Everything runs in your browser — nothing is uploaded.

How it works

Each formula takes the weight you lifted and the number of reps and extrapolates back to a single maximal rep. They agree closely at low reps and diverge as reps climb, which is why this tool shows every estimate and reports the average rather than hiding the disagreement. For the most trustworthy result, use a hard set of one to five reps; estimates from sets above ten reps drift because fatigue, breathing, and technique start to matter more than raw strength.

Reading the results

The percentage chart converts your estimated 1RM into the loads coaches program against — 5×5 work often sits near 80%, speed work near 60–70%, and a heavy single near 95–100%. The rep-max table flips that around: it tells you roughly what you could lift for 2, 3, 5, 8, or 10 reps. The warmup ramp steps you up to an 80% working set, and the plate loading line spells out exactly which plates to slide onto each side of the bar so you're not doing arithmetic between sets.

Worked example

Say you back-squat 100 kg for 5 reps. The formulas cluster around 112–117 kg, averaging about 115 kg. That means an 85% day would be roughly 97.5 kg, a 5RM sits near 100 kg (exactly what you lifted, a good sanity check), and to load a 92 kg working set on a 20 kg bar you'd put 25 + 10 + 1.25 kg per side.

Frequently asked questions