One Rep Max Calculator
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Rep maxes & percentages
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How to use your 1RM
Your one rep max is the anchor for most strength programs. Here's how to train from it, how the estimate works, and how to get a number you can trust.
1Train by percentage
Programs like 5/3/1 and most powerlifting plans set your working weights as a percentage of your max. Each range builds something different.
| % of 1RM | Reps | Builds |
|---|---|---|
| 90–100% | 1–3 | Peak strength |
| 80–90% | 3–6 | Strength |
| 70–80% | 6–10 | Strength and muscle |
| 60–70% | 10–15 | Muscle and endurance |
| 50–60% | 3–5 | Warm-ups, speed |
The percentage table above does the math for you. With a 300 lb max, 80% is 240 lb.
2Rate your set with RPE
RPE (rate of perceived exertion) scores a set by how many more reps you could have done. It turns a set you didn't take to failure into a useful estimate.
| RPE | Reps left in the tank |
|---|---|
| 10 | None, an all-out set |
| 9.5 | Maybe one |
| 9 | One |
| 8 | Two |
| 7 | Three |
| 6 or less | Four or more |
Not sure? Leave RPE at 10. Your estimate will be slightly conservative rather than too high.
3The seven formulas
No single formula fits every lifter, so the calculator averages seven well-known ones. w is the weight lifted and r is the reps.
They agree closely between 2 and 10 reps and drift apart beyond that, which is why the calculator flags high-rep sets.
4Get a better estimate
- Use a hard, recent set. A set close to failure from this week beats an easy set from last month.
- Stay between 2 and 10 reps. Heavy sets of 3 to 5 give the tightest estimates.
- Compare like with like. Paused and touch-and-go bench, or belted and beltless squats, give different maxes.
- Re-check every few weeks. An old max makes your percentages too light as you get stronger. The app keeps your current and best 1RM for every lift.
FAQ
What is a one rep max (1RM)?
The heaviest weight you can lift for one complete rep with good form. Most strength programs set working weights as a percentage of it.
How is my 1RM calculated?
We average seven formulas: Epley, Brzycki, Lombardi, Mayhew, McGlothin, O'Conner and Wathan. With RPE, the reps you had left are added first, so 5 reps at RPE 8 counts as 7.
How accurate is a 1RM calculator?
Most reliable from a heavy set of 2 to 10 reps. Past about 10 reps the formulas drift apart.
Should I test my true 1RM?
Not often. A true max is tiring and riskier, especially without a spotter. An estimate from a hard set of 3 to 5 is close enough for programming. Save true max attempts for meets or planned tests.
Does it work for squat, bench and deadlift?
Yes. It's most reliable for compound barbell lifts like the squat, bench press, deadlift and overhead press.
What is a training max?
A slightly reduced max that some programs use to set weights. Wendler's 5/3/1, for example, uses 90% of your 1RM, so a 300 lb max gives a 270 lb training max.
Is the One Rep Max app free?
Yes, it's free to download on iPhone and Android, with an optional subscription for extra features.
Stop guessing your max.
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