One-rep max calculator (1RM)
Estimate your 1RM — the most weight you could lift once — without having to risk actually testing it. Enter the weight and reps of a set you completed and we compute your 1RM with the three most-used formulas, plus a table of training loads by percentage.
Your estimated 1RM
92.5 kg
By each formula: Epley 93.5 · Brzycki 90 · Lombardi 94
Training loads (% of your 1RM)
88
95%
83.5
90%
78.5
85%
74
80%
69.5
75%
65
70%
60
65%
55.5
60%
Renzy logs your sets with progressive overload and suggests next session’s weight.
Estimate using the Epley, Brzycki and Lombardi formulas. Most reliable with sets of 1-5 reps. Never test a true 1RM without warming up and, ideally, a spotter.
How is 1RM calculated?
The 1RM is estimated from a submaximal set using the relationship between weight, reps and effort. We combine three validated formulas: Epley (1RM = weight × (1 + reps/30)), Brzycki (weight × 36/(37−reps)) and Lombardi (weight × reps^0.10), and show the average. It is most accurate with sets of 1-5 reps near failure; beyond 10-12 reps reliability drops. From your 1RM we compute typical training loads: 85-95% for max strength, 70-80% for hypertrophy, 60-70% for muscular endurance.
FAQ
What is 1RM?
The 1RM (one-rep max) is the most weight you can lift once with good form on an exercise. It is the reference for programming strength-training intensity by percentages.
Do I have to test a true 1RM?
No, and for most people it is not advisable — testing a true max carries injury risk. This calculator estimates it from a normal set (say 5 reps), which is much safer and almost as useful.
What percentage for muscle or strength?
For hypertrophy, mostly 70-80% of 1RM (8-12 reps). For max strength, 85-95% (2-5 reps). The table gives the exact kilos.
How often does my 1RM change?
It rises as you progress. Recalculate every 4-8 weeks or when you hit new set PRs.