One Rep Max Calculator
Enter a weight you lifted and how many reps you got. You will get your estimated one rep max (1RM) from six proven formulas, the full percentage table, and your training max — instantly, in kg or lbs.
Calculate your 1RM
| Formula | Estimated 1RM |
|---|---|
| Epley | — |
| Brzycki | — |
| Lombardi | — |
| Mayhew | — |
| O'Conner | — |
| Wathan | — |
Percentage table
Working weights based on your estimated 1RM. The reps column is an estimate of how many reps most lifters can do at that percentage.
| % of 1RM | Weight | Est. reps |
|---|
Training Max (90% of 1RM)
Your training max is —. Programs like 5/3/1 set every working weight as a percentage of this number instead of your true max. Training with 90% leaves a buffer for bad days, keeps bar speed high, and still drives progress — most lifters who stall are training too close to their true max too often.
What is a one rep max?
Your one rep max — written as 1RM — is the heaviest weight you can lift for one full repetition of an exercise with good technique. It is the anchor number for strength training: working weights, program percentages and progress tracking all come back to it. A squat 1RM of 180 kg, for example, means an 80% training day is 144 kg without any guessing.
Testing a true 1RM is demanding and carries some risk, especially for newer lifters. That is why most lifters estimate it from a hard submaximal set — lift a weight for 3–5 reps, and a formula converts that performance into an estimated max. The estimate is close enough to program training, and far safer than maxing out every few weeks.
How this calculator works
There is no single agreed formula, so this calculator runs your set through six established equations and shows all of them plus their average:
| Formula | Equation |
|---|---|
| Epley (1985) | w × (1 + reps ÷ 30) |
| Brzycki (1993) | w × 36 ÷ (37 − reps) |
| Lombardi (1989) | w × reps0.10 |
| Mayhew et al. | w × 100 ÷ (52.2 + 41.9 × e−0.055 × reps) |
| O'Conner et al. (1989) | w × (1 + 0.025 × reps) |
| Wathan (1994) | w × 100 ÷ (48.8 + 53.8 × e−0.075 × reps) |
Sets of 2–6 reps give the most reliable estimates. Above 10 reps the formulas start to disagree because muscular endurance and pacing affect the result more than raw strength — treat high-rep estimates as a rough guide. If you train with RPE, the RPE calculator can estimate your max from a set rated by effort instead.
How to use your percentages
The percentage table above turns your 1RM into a training plan. As a general guide: 90–100% builds maximal strength in singles and doubles; 80–90% is the classic strength zone for sets of 3–6; 70–80% suits volume work of 6–10 reps; and below 70% is for technique practice, speed work and warm-ups. Compare your numbers against typical lifter levels on the strength standards page, and if you compete, convert your total into a DOTS score or a Wilks score to compare against other weight classes.
Safety notes
Estimating beats testing for most lifters most of the time. When you do attempt a heavy single: warm up with progressively heavier sets, use a spotter or safety arms for squats and bench, and stop the attempt if your technique breaks down. A calculated max is a planning tool — it does not mean you should load that weight on your first try.
Frequently asked questions
What is a one rep max (1RM)?
Your one rep max is the maximum weight you can lift for a single repetition of an exercise with good form. It is the reference number used to set training percentages for squats, bench press, deadlift and other barbell lifts.
How accurate is a one rep max calculator?
Estimates from low-rep sets (2–5 reps) are usually within about 2–5% of a tested max. Accuracy drops as reps increase, because endurance and technique start to matter more than pure strength. Sets above 10 reps are rough estimates only.
Which 1RM formula is the most accurate?
No single formula wins for everyone. Epley and Brzycki are the most widely used; research comparisons often find Mayhew and Wathan close for trained lifters. That is why this calculator shows all six formulas plus their average, so you can pick the estimate that matches your own tested maxes.
What is a training max?
A training max is typically 90% of your one rep max. Many programs (such as 5/3/1) base their working percentages on a training max instead of a true max, which keeps training weights achievable even on bad days and leaves room for steady progression.
Should beginners test a true one rep max?
Beginners are usually better off estimating their 1RM from a hard set of 3–5 reps instead of attempting a true single. It is safer, needs less technical skill, and is accurate enough to program training.
How often should I recalculate my 1RM?
Recalculate every training block (roughly every 4–8 weeks) using a recent hard set, or whenever your working weights start feeling noticeably easier or harder than the percentages suggest.