How do you calculate your one-rep max (1RM)?
Short answer
Lift a challenging but manageable weight for 3 to 8 reps with good form, then plug it into a formula instead of testing a true single-rep max. A 185 lb bench press for 5 reps works out to about 216 lb by the Epley formula and about 208 lb by the Brzycki formula, averaging to roughly 212 lb. Use that estimate, not a maximal lift, to set your training weights, testing a true 1RM carries real injury risk and isn't necessary for most training goals. This is general fitness guidance, not medical advice.
One-rep max formulas
Epley: 1RM = w x (1 + r / 30); Brzycki: 1RM = w x 36 / (37 - r)
- •w is the weight lifted, in pounds or kilograms
- •r is the number of clean reps completed, most accurate between about 2 and 10
- •many lifters average the two formulas for a middle-ground estimate
Why estimate instead of test a true max
A true one-rep max is the heaviest weight you can lift for exactly one rep with correct form. Finding it by trial and error means working up through near-maximal attempts until you fail, which is where most injuries around heavy lifts happen, a missed bench rep without a spotter or safety bars, a rounded back on a max deadlift attempt, a knee that buckles under a max squat.
Estimating from a submaximal set avoids that. Lift a weight you can move for a genuine 3 to 8 reps with clean form, feed the weight and rep count into a formula, and you get a number close to your true max without ever approaching failure. For almost every training purpose, programming percentages, tracking progress, deciding how much to load the bar, the estimate is all you need.
The two formulas: Epley and Brzycki
Epley: 1RM = w x (1 + r / 30). Brzycki: 1RM = w x 36 / (37 - r). Both take the weight you lifted (w) and the reps you completed (r) and project what you could have done for one rep.
They're built differently and don't always agree. Epley assumes a fairly steady drop-off in reps as weight increases; Brzycki comes from a lookup table originally built for sets of up to about 10 reps. At low rep counts (2 to 5) the two formulas usually land within a few pounds of each other. Past about 8 to 10 reps they diverge more, and Epley tends to run a little higher. Many lifters simply average the two for a middle-ground number.
Worked example: 185 lb bench press for 5 reps
Say you bench 185 lb for 5 clean reps.
Epley: 185 x (1 + 5/30) = 185 x 1.1667 = 215.8, which rounds to about 216 lb.
Brzycki: 185 x 36 / (37 - 5) = 185 x 36/32 = 185 x 1.125 = 208.1, or about 208 lb.
Average the two: (216 + 208) / 2 = 212 lb. That 212 lb figure is your working estimate of a true one-rep max, a number you never actually had to attempt.
Turning your estimate into a training plan
The whole reason to know your 1RM is to program percentages of it for specific goals. Using the 212 lb estimate from above:
- Strength (3 to 5 reps): about 85 to 90% of 1RM = 180 to 191 lb
- Hypertrophy (6 to 10 reps): about 75 to 85% of 1RM = 159 to 180 lb
- Endurance (12 to 15 reps): about 60 to 70% of 1RM = 127 to 148 lb
How accurate are these formulas, and where they break down
Both formulas are most accurate in the range they were built for, roughly 2 to 10 reps. Below that, at 1 to 3 reps, the estimate sits close to a real max because you're barely extrapolating. Above about 10 reps, accuracy drops off, because the relationship between reps and percentage of max stops being linear, fatigue and technique breakdown start to matter more than raw strength, and neither formula accounts for that.
There's also person-to-person variation. Lifters with a higher proportion of fast-twitch muscle fiber tend to fatigue faster at high reps, so a formula run off a high-rep set underestimates their true max; slow-twitch-dominant lifters hold up longer at higher reps, so it can overestimate theirs. The lower your rep count when you test, the less this matters, which is another reason to stay in the 3 to 8 rep range.
Common mistakes
A few habits either inflate the estimate or put lifters at unnecessary risk. Round both back down to something safer and more accurate before you program off the number.
- Testing a true 1RM without a spotter or safety bars. A failed heavy attempt on a bench, squat, or overhead lift is where serious injuries happen; a submaximal-set estimate gets you a usable number without that risk.
- Plugging in a set of more than about 10 reps. Both formulas lose accuracy at high rep counts, so a 15-rep set will overstate or understate your real max more than a 5-rep set will.
- Treating one estimate as permanent. Strength changes over weeks of training, so a number from two months ago won't reflect where you are now. Recalculate periodically rather than programming off an old figure.
- Counting a rep that wasn't clean. A partial-range press or a bounced rep inflates the rep count without representing real strength, which pushes the formula's result higher than your actual capability.
Frequently Asked Questions
Which formula is more accurate, Epley or Brzycki?+
Neither is definitively more accurate across the board, they're built from different assumptions and agree closely at low rep counts (2 to 5), diverging more as reps climb toward 10. Epley usually estimates a bit higher at higher rep counts; Brzycki tends to run a bit more conservative. Averaging the two, as in the worked example above, is a reasonable way to split the difference rather than trusting one exactly.
How many reps should I do to estimate my 1RM?+
Aim for 3 to 8 reps at a weight that's genuinely challenging by the last rep but still done with clean form. Lower rep counts (2 to 3) get you closer to a true max with less extrapolation, but they're also heavier and carry more of the fatigue and technique risk you're trying to estimate around in the first place. A 5-rep set, like the worked example, is a common sweet spot.
Should beginners test or estimate their one-rep max?+
Estimate, not test. New lifters haven't yet built the technique and bar-speed awareness to safely judge when a heavy attempt is about to fail, which raises injury risk right when you're least equipped to handle it. An estimate from a clean submaximal set gives a usable training number without that exposure, and it's accurate enough to program a first several months of training.
How often should I recalculate my one-rep max?+
Every 4 to 8 weeks, or after finishing a training block, is a reasonable cadence for most lifters. Strength doesn't meaningfully change session to session, so there's no need to retest constantly, and doing so just adds fatigue for no benefit. Recalculate once you've been adding weight or reps for a few weeks and want your training percentages to reflect the new baseline.
Sources & further reading
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