What is a 1RM (one-rep max)?

Updated October 25, 2026

Short answer: 1RM means one-repetition maximum, the heaviest weight you can lift for one full rep with good form. It is sometimes typed 1 RPM or 1 rm, but it is the same thing. Strength programs use it as a reference point: a workout of 5 sets at 80% means 80% of your 1RM for that lift.

Example: estimating a 1RM from a set of 5

You do not have to lift your max to know roughly what it is. Say you bench 100 kg for 5 reps. The Epley formula estimates a 1RM from a set like this:

• 1RM = weight × (1 + reps ÷ 30)
• 100 × (1 + 5 ÷ 30) = 116.67 kg

So a lifter who can bench 100 kg for 5 could probably bench about 116.67 kg once. It is an estimate, not a promise. For your own numbers and other formulas, use the 1RM calculator.

Tested vs estimated 1RM

There are two ways to get the number, and they answer slightly different questions.

A tested max is real, but it costs a session and needs a spotter or safety arms. An estimate is free, but different formulas give different answers, and none of them is reliable for sets of 15 or 20.

1RM vs a rep PR

A 1RM is a single. A rep PR is the most you have lifted for some other number of reps, such as your best set of 5. Both are personal records, and a rep PR can be turned into an estimated 1RM like the example above. The guide what is a PR in the gym covers rep PRs and weight PRs in full.

What LoadPR calls your current PR

In the LoadPR app, the current PR of a lift is the heaviest weight you have logged for it, at any number of reps. It is not an estimate: if your heaviest bench entry is 225 lb for 3, your current PR is 225 lb. The app estimates the 1RM separately with the Epley formula, which it writes as weight × (1 + 0.0333 × reps), so 200 lb for 3 reps comes to an estimated 219.98 lb. With LoadPR+ the estimate appears as its own line on the full progress chart. The percentage wheel works from your current PR or from any weight you type, so you can type your 1RM if you want percentages of it. More in PR tracking.

Why programs use a percentage of your 1RM

Percentages let one plan fit every lifter. A program that says 80% gives a 140 kg squatter and a 60 kg squatter the same effort. For a 140 kg 1RM:

The exact number is rarely loadable, so you round to the nearest weight your plates can make. The 1RM percentage calculator does that for the whole table.

Every lift has its own 1RM

Your squat, bench press, deadlift and overhead press each have a separate 1RM, and so do variations such as a paused bench or a front squat. Keep them apart in your log. A 1RM also belongs to its conditions: a max with a belt and a max without one are different numbers, and so is a max in kg compared with one rounded to pounds.

Mistakes with a 1RM

• Counting a rep that was not a full rep. A squat above depth or a bench that bounced is not a 1RM.
• Estimating from very long sets. A set of 15 says more about endurance than about your max.
• Mixing formulas. Epley and other formulas give slightly different estimates. Pick one and stay with it so your numbers compare. How 1RM is calculated sets them side by side.
• Training from an old max. A 1RM from months ago may be too high or too low now. Re-estimate from a recent set.
• Treating the estimate as a target. An estimated 1RM is a planning number, not a weight you have to hit.