Free tool
One Rep Max (1RM) Calculator
Enter a weight you can lift for a given number of reps and we'll estimate your true one-rep max, plus the 90%, 80% and 70% marks most training programmes are written against.
What this number can’t tell you
One number, one day. The paid report turns it into a plan — the sections it feeds:
- 12-week program16 min
- Weekly checklists1 min
- Playbooks4 min
How we compute this
We use the Epley formula: 1RM = weight × (1 + reps ÷ 30). Lift 60 kg for 5 reps and it estimates a 70 kg one-rep max — you didn't have to load the bar and grind out a single all-out rep to find out.
The 90%, 80% and 70% marks below are common training-percentage references — many strength and hypertrophy programmes prescribe work sets as a percentage of 1RM rather than an absolute weight, so once you know your estimate you can read straight off it.
The formula is most accurate at low-to-moderate rep counts (roughly 10 and under) because fatigue and technique breakdown distort the relationship between reps and load at very high rep counts — treat an estimate from a 12-rep set as a rougher guide than one from a 3-rep set.
Questions people ask
For sets of 10 reps or fewer, Epley gives a good estimate — typically within a few kg of a true tested max. Several similar prediction formulas exist (Brzycki, Lombardi, and others) and they usually agree within a small margin of each other in that rep range. Accuracy drops off the further you get past 10 reps, since fatigue and form breakdown start to distort the reps-to-load relationship.