One Rep Max
Estimate your 1RM from any set โ with the percentage training table.
About this calculator
Weight and reps from any hard set in; your estimated one-rep max out, computed with both classic formulas (Epley and Brzycki, averaged for the headline), plus the full percentage table โ because programs prescribe "5ร5 at 80%" and this is where the 80% comes from.
Using estimates like a coach
The formulas agree tightly in the 2โ8 rep range and drift beyond it, which is why the calculator declines politely past 12 reps โ a 20-rep set predicts a max about as well as a horoscope. The estimate assumes the set was near failure: five easy reps say little. What estimated maxes are FOR: programming loads without the injury risk and fatigue cost of actual max testing โ most programs never test a true 1RM at all. Rep-range rules of thumb encoded in the table: 1โ5 reps builds strength, 6โ12 size, 13+ endurance, with generous overlap. Track the trend over months in the habit tracker, and convert plates with kg โ lb. Estimated maxes are for planning โ test real ones with a spotter.
Frequently asked questions
How accurate are 1RM formulas?
Within ~5% when estimated from a hard set of 2-8 reps. Accuracy degrades with higher reps โ past 12 the formulas drift badly, so the calculator asks for a heavier set instead.
What's the difference between Epley and Brzycki?
Two curve fits to the same phenomenon: Epley is linear in reps, Brzycki hyperbolic. They agree closely in the useful range; the headline number averages them.
What percentage should I train at?
Depends on the goal: 80-90% for strength work in low reps, 65-75% for hypertrophy ranges, 60% for technique and warm-ups. The table converts your estimate into all of them.
Should I actually test my 1RM?
Rarely โ estimates cover programming needs without the injury and fatigue cost. If you do test, use a spotter and full rest days; maxing out is an event, not a workout.