MyGymCalcWhat is a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can move for a single repetition with good form. It is the yardstick strength programmes are built on: percentages of 1RM tell you how hard each set should be, so training can be planned instead of improvised.
Testing a true max has a cost — heavy singles beat up joints, drain the nervous system and can stall a training week. Estimating it from a submaximal set gives you a number close enough to program with, and you can repeat it safely every few weeks.
Which formulas do we use?
We show two of the most widely published estimates side by side:
- Epley:
1RM = weight × (1 + reps ÷ 30)— the common default, accurate for sets of roughly 1–10 reps. - Brzycki:
1RM = weight × 36 ÷ (37 − reps)— a slightly more conservative estimate that holds up well for heavy sets of 1–6 reps.
Both come from real-world testing rather than guesswork, and for a set close to failure they usually land within 5% of a tested max. The wider the rep range, the more the two formulas drift apart — treat the gap as a confidence band.
How to use your result
Enter a hard set with good technique: for example 100 kg for 5 reps. The results give you an Epley estimate and a Brzycki estimate, followed by a table running from 50% to 100% of that max.
Programme from the table: heavy triples at 85–95% for strength blocks, sets of 6–12 at 70–80% for hypertrophy, and lighter weights for warm-ups and speed work. Log the estimate next to the date so you can watch it climb.
Re-estimate every time a weight that used to feel like a 4-rep set starts feeling like a 6-rep set. That change is progress, even when you never touch a true max.
Choosing weights from the table
Take the estimated max and work down from 100%: 90–95% for heavy singles and doubles in a strength block, 80–85% for triples and fours, 70–80% for the classic 6–12 hypertrophy range, and 50–65% for warm-ups, technique work and speed days.
Round each percentage to the nearest load you can actually build with your plates, then keep it consistent week to week so the numbers stay comparable. A simple logbook — date, weight, reps, estimated max — turns those rounded loads into proof that the programme is working.