Open almost any structured lifting program and you'll hit an instruction like "squat 5 sets of 3 at 85%." That percentage refers to your one-rep max, or 1RM — the heaviest weight you can lift once with good form. Here's the useful part: you don't have to actually lift that weight to know what it is. Two well-established formulas can estimate your 1RM from an everyday work set: Epley (1RM = weight × (1 + reps ÷ 30)) and Brzycki (1RM = weight × 36 ÷ (37 − reps)). This guide walks through the exact math, when an estimate beats a true test, and how to turn the number into smarter training.
What a one-rep max actually is
Your one-rep max is the maximum weight you can lift for a single repetition of a given exercise with proper technique. The "proper technique" part matters: a grinding, back-rounding deadlift that barely locks out measures what your spine tolerated that day, not your strength.
A 1RM is exercise-specific — your squat, bench press, and deadlift each have their own — and it isn't fixed. It rises as you train, and it dips when you're sleep-deprived, under-fueled, or coming back from a layoff. Think of it as a snapshot, not a permanent label.
There are two ways to find it: test it directly by working up to a maximal single, or estimate it from a set of multiple reps using a prediction formula. For most people, most of the time, the estimate is the better tool — more on why below.
Why your 1RM matters for programming
The reason coaches care about 1RM isn't bragging rights. It's that training intensity — how heavy a weight is relative to your capacity — is one of the main levers that determines what adaptation you get. Strength and conditioning textbooks, including the National Strength and Conditioning Association's (NSCA) Essentials of Strength Training and Conditioning, prescribe loads as percentages of 1RM because "185 pounds" means something completely different to a beginner and a seasoned lifter, while "80% of your max" scales to both.
The standard NSCA load assignments by training goal look like this:
- Maximal strength: 85% of 1RM or heavier, for sets of 6 reps or fewer.
- Power (speed-strength): 80–90% of 1RM for single-effort events (1–2 reps) and 75–85% for multiple-effort work (3–5 reps), stopping well short of failure so bar speed stays high.
- Muscle growth (hypertrophy): 67–85% of 1RM, for sets of 6–12 reps.
- Muscular endurance: 67% of 1RM or lighter, for sets of 12 or more reps.
Without a 1RM figure, those percentages are unusable. With one — even an estimated one — you can pick working weights deliberately instead of guessing. If you'd rather skip the arithmetic, our one-rep max calculator runs the formulas below for you and shows your percentage breakdowns in one step.
The Epley and Brzycki formulas
Many 1RM prediction equations exist, but two have become the standards, and most calculators you'll find online run on one of them.
The Epley formula
Published by University of Nebraska strength coach Boyd Epley in 1985:
1RM = weight × (1 + reps ÷ 30)
In plain language: take the number of reps you completed, divide by 30, add 1, and multiply the result by the weight you lifted. Each extra rep adds one-thirtieth of the lifted weight — about 3.3% — to the estimate.
The Brzycki formula
Published by strength coach Matt Brzycki in 1993:
1RM = weight × 36 ÷ (37 − reps)
Here you subtract your rep count from 37, divide 36 by that result, and multiply by the weight lifted.
A neat quirk of the math: at exactly 10 reps, both formulas multiply your lifted weight by 4/3 and give identical answers. Below 10 reps, Brzycki reads slightly lower (more conservative); above 10 reps, it reads slightly higher. In the 2–5 rep range where these estimates are most trustworthy, the two land within about 4% of each other — close enough that either works fine.
A worked example
Say you bench press 185 pounds for 5 solid reps, with maybe one more rep left in you.
Epley: 185 × (1 + 5 ÷ 30) = 185 × 1.167 ≈ 216 pounds
Brzycki: 185 × 36 ÷ (37 − 5) = 6,660 ÷ 32 ≈ 208 pounds
Split the difference and call your estimated 1RM about 210–215 pounds. Now the percentages become actionable: a hypertrophy day at 75% means working sets around 160 pounds for sets of about 10, while a strength day at 87% puts roughly 185 on the bar for tough sets of 5 — which checks out, because that's exactly the set you just did.
Why a 2–5 rep set beats a set of 10 or more
Prediction formulas are at their best when the rep count is low. Research comparing predicted and measured maxes — including a 2006 study by Reynolds and colleagues in the Journal of Strength and Conditioning Research that tested 5, 10, and 20-rep maxes on the bench press and leg press — finds that estimates built from sets of about 5 reps track true 1RM closely, and that accuracy worsens as the rep count climbs toward 10 and beyond.
The reason is physiological. A heavy triple is mostly a test of maximal strength — the same quality a 1RM measures. A set of 15, by contrast, is heavily influenced by muscular endurance, and endurance varies a great deal between people. Two lifters with the same 1RM can get very different rep counts with the same submaximal weight; feed those numbers into a formula and you'll get two very different "maxes" for two equally strong people.
Practical takeaway: estimate from your heaviest recent set of 2–5 reps, taken close to failure (about one rep left in the tank). Don't bother plugging in your 20-rep leg press.
%1RM and reps: a reference table
This table shows roughly how many reps a trained lifter can complete at each percentage of 1RM, following NSCA conventions. Read it in either direction — to pick a working weight from your max, or to sanity-check an estimated max against a set you've actually done.
| % of 1RM | Reps typically possible | Common training use |
|---|---|---|
| 100% | 1 | Max testing |
| 95% | 2 | Maximal strength |
| 93% | 3 | Maximal strength |
| 90% | 4 | Maximal strength |
| 87% | 5 | Strength |
| 85% | 6 | Strength / hypertrophy |
| 83% | 7 | Hypertrophy |
| 80% | 8 | Hypertrophy |
| 77% | 9 | Hypertrophy |
| 75% | 10 | Hypertrophy |
| 70% | 11 | Hypertrophy |
| 67% | 12 | Hypertrophy / endurance |
| 65% | 15 | Muscular endurance |
Adapted from the NSCA Training Load Chart (after Landers, 1984) and Essentials of Strength Training and Conditioning (4th ed.). These are population averages — your own rep count at a given percentage may differ by a rep or two, especially on smaller exercises.
Should you ever test a true 1RM?
Sometimes, yes — but it's a tool with a narrow job. A true max-out makes sense for experienced lifters whose technique holds up under maximal load, for powerlifters who compete on singles, and at the end of a training block when you want a definitive benchmark. If you do test, do it properly: a thorough warm-up, small progressive jumps toward the max, safety pins or spotters in place, and a hard stop the moment form breaks down.
Estimation is the smarter default when you're newer to lifting, training alone, returning after time off, or simply mid-program and curious. A missed maximal attempt carries injury risk that a hard set of 3 does not, and the estimate delivers most of the useful information for a fraction of the strain. Plenty of very strong people never test a true single.
One honest caveat: this guide is educational, not medical advice. If you have a heart condition, high blood pressure, a hernia, or any injury history that makes near-maximal straining risky, talk with your healthcare provider before chasing heavy singles.
Putting the number to work
Once you have an estimated 1RM, use it: anchor your working weights to the percentage ranges above, train consistently, and re-estimate every 4–12 weeks — ideally from the same lift and rep range so you're comparing like with like. Watching your estimated max climb across training blocks is one of the most motivating metrics in lifting.
And remember that the lifting is only half the equation. Strength is built between sessions, which means eating enough protein — our protein intake calculator gives you a research-based daily target — and enough total food to support recovery, which you can gauge with the TDEE calculator. Heavy percentages on paper only turn into strength when recovery keeps pace.
Sources: National Strength and Conditioning Association (NSCA) Training Load Chart; Haff GG, Triplett NT (eds.), Essentials of Strength Training and Conditioning, 4th ed., Human Kinetics; Landers J, "Maximum based on reps," NSCA Journal, 1984; Epley B, Poundage Chart, Boyd Epley Workout, University of Nebraska, 1985; Brzycki M, "Strength testing — predicting a one-rep max from reps-to-fatigue," Journal of Physical Education, Recreation & Dance, 64(1), 1993; Reynolds JM, Gordon TJ, Robergs RA, "Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry," Journal of Strength and Conditioning Research, 20(3), 2006.