What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift once with good form. Testing it directly is tiring and carries some risk, so most lifters estimate it from a set of several reps with a lighter weight. Training plans are often written as a percentage of 1RM, which the table turns into weights for you.
Example: benching 185 lb for 5 reps gives an estimated 1RM of about 214 lb (the average of the three formulas). Training at 80% of it means sets with about 171 lb.
The formulas
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
- Lombardi: 1RM = weight × reps0.1
They agree closely at low reps and drift apart above about 10, where endurance starts to matter more than strength.
Training by percentage
- 90% and above: maximal strength, 1 to 3 reps
- 75% to 85%: strength and muscle growth, about 5 to 8 reps
- 60% to 75%: muscle growth and endurance, about 10 to 15 reps
Frequently asked questions
Is it safe to test a true 1RM?
With a warm-up, good technique and a spotter or safety bars, experienced lifters do it regularly. Beginners are better off using an estimate.
Does it work for every exercise?
Best for big compound lifts such as the squat, bench press and deadlift. For small isolation exercises the estimates are less reliable.
Why does my real 1RM differ?
Some people are stronger for one rep and others for many. Use the estimate as a starting point and adjust from how your sets feel.