CEILING
Your estimated one-rep max and every working percentage under it, from a set you already did. Needs one hard set — weight and reps. No body stats required.
The max you never have to attempt
An estimated one-rep max, reverse-engineered from a set you already did. Take a hard set of five, hand it over, and get back the number a true max attempt would have given you — without the true max attempt, which is the part that gets people hurt.
Programme from the percentage table, not from the top figure. Strength work lives at 85–95 percent for low reps; hypertrophy sits around 67–80 for sets of eight to twelve; technique work belongs below 60.
Re-run it every four to six weeks off a fresh set. A max from March is a historical document, not a training input.
Garbage in, confident garbage out. Use a set taken close to failure — one or two reps left, no more — with clean technique on every rep and no help from a spotter.
Three to six reps is the sweet spot for accuracy. A grinding set of ten with a bouncing bar and a rounding back does not describe your strength; it describes your optimism.
Both formulas were built on sets of ten or fewer, and above that they inflate — the tool flags it when you go past ten and refuses to guess past twelve.
They also assume every lift behaves the same way, and lifts do not. Deadlifts tend to come in under the estimate because they start from a dead stop with no stretch reflex; well-grooved bench presses often beat it. Rep endurance is individual too: two men with the same true max can put up different numbers for five.
Treat the output as a planning figure. A calculated max is not a max you have — it is a max the arithmetic thinks you might have, on a good day, with a good warm-up.
Estimates, not diagnoses. These figures describe averages and your body is not one. Nothing here treats, cures or prevents anything — and if you are managing a health condition, taking medication, or working through a relationship with food, talk to a professional before acting on a number a website gave you.