What is a one rep max?
Your one rep max, or 1RM, is the heaviest weight you can lift for one full repetition with proper form. It is the standard way to measure maximal strength on lifts like the squat, bench press and deadlift.
Testing a true max is demanding and can be risky without a spotter. That is why many lifters use a 1 rep max calculator instead: you lift a lighter weight for several reps, and a formula estimates what you could do for a single.
How to calculate your 1RM manually
- Warm up well, then do a hard set of 2 to 10 reps with good form.
- Note the weight and the number of reps you completed.
- Put them into a formula such as Epley: weight ร (1 + reps รท 30).
Why six formulas?
Each formula was fit to different groups of lifters and lifts, so they disagree a little. Epley and Brzycki are the best known. Lombardi, O'Conner, Mayhew and Wathan are other published equations. At low reps they are close together. As reps climb, the gap grows.
Averaging them is a simple way to avoid relying on one equation. If you prefer one formula, you can read each result in the list above.
Percentage chart for training
Coaches often prescribe work as a percentage of 1RM. The chart on this page shows the weight for each percentage from 100% down to 50%, with typical rep ranges.
| % of 1RM | Typical reps | Common use |
|---|---|---|
| 90-100% | 1-4 | Maximal strength |
| 80-90% | 4-8 | Strength |
| 65-80% | 8-15 | Muscle growth |
| 50-65% | 15+ | Endurance, warm-ups |
The rep counts are approximate. People differ a lot, and a lift you are skilled at will allow more reps at the same percentage.
How accurate are the estimates?
Estimates are best from sets of about 2 to 10 reps and get shakier above 12, because endurance, fatigue and technique start to matter more than raw strength. If you did more than 12 reps, the calculator shows a warning.
Also remember that an estimate depends on how honest the set was. Stopping 3 reps short of failure and counting it as a max set will under-predict your 1RM.
Safety tips for testing a max
- Warm up with several progressively heavier sets.
- Use a spotter or safety bars for squats and presses.
- Do not test a max when tired, sore or in pain.
- Many people never need a true max. Training with estimated percentages is a safer option.
Using your 1RM in a program
Once you know your estimate, pick a training percentage that matches your goal. For example, a set of 5 at about 85% builds strength, while sets of 10 at about 75% suit muscle growth. Retest or recalculate every few weeks as you get stronger, and use a recent set rather than an old one.