One-rep max calculator
Estimate your strength from a lighter set — no white-knuckle max attempts required.
Your one-rep max is a handy strength benchmark — but you don't need to actually attempt a max to know it. You can estimate it from a set you can already do comfortably, then use it to set smart training weights.
The short answer: estimate your 1RM from a lighter set (weight and reps), then train with percentages of it — around 65–75% for muscle-building, 80%+ for strength. You never have to test a true max to train effectively.
Estimate your one-rep max
One-Rep Max
Estimate your max and the loads to train at.
| Goal | % of max | Load |
|---|---|---|
| Power | 90% | 142 lbs |
| Strength | 85% | 134 lbs |
| Muscle (hypertrophy) | 75% | 118 lbs |
| Endurance | 65% | 102 lbs |
Let’s program your strength work safely.
A note on doing it safely
Estimates are most reliable in the 2–10 rep range, and they assume solid technique — grinding out sloppy reps inflates the number and the risk. If you're newer to lifting, estimate from a comfortable set rather than chasing a true max, and stop a set when your form starts to break down.
Common questions
What is a one-rep max (1RM)?
Your one-rep max is the most weight you can lift for a single repetition of an exercise with good form. It is a common way to measure strength and to set training loads, since many programs prescribe weights as a percentage of your 1RM.
How is a one-rep max calculated?
You can estimate it from a set you actually did. A widely used formula (Epley) is: weight × (1 + reps ÷ 30). So 100 lbs for 5 reps estimates about 117 lbs. Estimates are most accurate in the 2–10 rep range — the higher the reps, the rougher the estimate.
Should beginners test their true one-rep max?
Usually not. Attempting a true max is most useful for experienced lifters and is safest with a coach or spotter. Most people are better off estimating their 1RM from a comfortable set of 3–8 reps, which gives plenty of information to train from without the injury risk.
How do I use my 1RM to train?
Programs often target a percentage of your 1RM: roughly 65–75% for muscle-building rep ranges and 80%+ for heavier strength work. Recalculate as you get stronger. The number is a guide, not a test you need to pass — good form always comes first.
This is general education, not medical advice. If you're new to strength training or have a health condition, check with a professional before lifting heavy.