How to Estimate Your 1RM Without Maxing Out

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You do not need to scare yourself to know your numbers

A true one-rep max attempt is a whole production. You need a good day, a spotter you trust, a warm-up that threads the needle between fresh and primed, and the willingness to load more weight than you have ever lifted and find out what happens. For most of us, most of the time, that is a terrible trade. You risk injury and a bad day to get a number that is stale by next month anyway.

The alternative is older than most lifters: take a submaximal set, plug the weight and reps into a formula, and get a 1RM estimate accurate enough to program from. LeSuer and colleagues validated this approach directly back in 1997, testing seven prediction equations against actual max tests in 67 lifters across the bench press, squat, and deadlift. Correlations ran above 0.95 across the board. You can read a good modern survey of how these equations hold up on arXiv, which walks through the LeSuer validation and everything since. The short version: the math works, provided you stay in the right rep range.

The four formulas worth knowing

Every formula takes your working weight and your reps and extrapolates to a predicted max. They disagree with each other a little, and that disagreement is the point of knowing more than one.

Epley (1985): weight x (1 + reps / 30). The most widely used formula, and the one most calculators default to. Best in the 2 to 8 rep range. Bench 225 for 5 and Epley says your max is 225 x (1 + 5/30) = 262.5 pounds.

Brzycki (1993): weight x 36 / (37 - reps). Slightly more conservative than Epley once reps climb, and most accurate in the 1 to 6 range. Same 225 x 5 gives 225 x 36 / 32 = 253.1 pounds.

O’Connor (1989): weight x (1 + 0.025 x reps). A gentle per-rep increment, solid in the 2 to 8 range. For 225 x 5: 225 x 1.125 = 253.1 pounds. Notice Brzycki and O’Connor agree here; they often do at low reps.

Lombardi (1989): weight x reps^0.10. The only one that scales exponentially instead of linearly, and it behaves best in the 2 to 10 range. For 225 x 5: 225 x 5^0.10 = 264.3 pounds.

Run all four on the same set and you get a band, not a single number. That band is more honest than any one formula pretending to be exact.

The rep range is the whole game

The formulas are only as good as the set you feed them. The pattern across every validation study is the same: accuracy is excellent near your max and degrades as reps climb.

1 to 5 reps: high confidence. The formulas converge within a few percent of your true max. This is where you should be testing.
6 to 10 reps: moderate confidence. Useful, but if the number matters for programming, retest heavier.
11 to 15 reps: rough guideline territory. The formulas start diverging from each other and from reality.
15+ reps: do not base programming decisions on this. You are extrapolating from a set that has almost nothing to do with maximal strength.

Reynolds and colleagues showed this cleanly in 2006: a 5RM test predicted 1RM with near-perfect accuracy, and predictions fell apart at 10RM and 20RM. The closer your test set is to a max, the better the estimate. Revolutionary, I know. But it means your “test” can just be a heavy set of 3 to 5, which is a normal training day, not a production.

The deadlift exception

Here is the quirk most online calculators will not tell you: every one of these formulas underestimates the deadlift, by roughly ten percent. LeSuer’s team found it across all the equations they tested. The deadlift has a longer range of motion and a different strength curve than the squat or bench, and the submaximal rep math does not capture the lockout the way it captures the rest of the lift.

The practical fix is a rule of thumb, not a law of physics: multiply your deadlift estimate by 1.10. Calculator says 405, your real max is probably sitting around 445. It will not be exact, but it will be closer than the uncorrected number, and closer is the whole point of estimating in the first place.

Sharpen it with RPE

If you know how hard the set felt, you can squeeze more accuracy out of the same numbers. Our RPE guide covers the scale in full; the short version for this article is the reps-in-reserve adjustment:

effective reps = actual reps + (10 - RPE)

Five reps at RPE 8 means two were left in the tank, so you treat it as seven effective reps and run the formulas on that. It is a small correction that matters most exactly when you need it: on days you stopped short of failure and still want a usable number.

Turning the estimate into training weights

Nobody programs at 100 percent every session. Most strength programs work off a training max, usually 85 to 90 percent of your true or estimated max, and build the week’s percentages from there. The classic layout looks like this:

Percentage	Use case
65%	Warm-up sets, volume work
70%	Hypertrophy sets, 8 to 12 reps
75%	Strength-endurance, 6 to 8 reps
80%	Strength work, 4 to 6 reps
85%	Heavy practice, 2 to 3 reps
90%	Training max in 5/3/1 and similar programs
95%	Peaking phase, 1 to 2 reps

The training max is a buffer with a purpose. When you can hit all your prescribed reps at 90 percent for the full cycle, you bump the training max up and run it again. Progress without ever needing a true max test. Our 8-week powerbuilding program runs on exactly this structure if you want to see it in action.

A worked example

Say you squat 275 pounds for 3 reps at RPE 9:

Effective reps: 3 + (10 - 9) = 4
Epley: 275 x (1 + 4/30) = 311.7 pounds
Brzycki: 275 x 36 / 33 = 300.0 pounds
O’Connor: 275 x (1 + 0.025 x 4) = 302.5 pounds
Lombardi: 275 x 4^0.10 = 315.9 pounds
Average: about 307.5 pounds
Training max at 90 percent: about 276.8 pounds, call it 277

Your working weights for the week then fall out of the table: 221 pounds at 80 percent, 235 at 85 percent, 249 at 90 percent. Round to whatever plates your gym actually has. The formulas do not care about your ego; they care about proximity, and 220 versus 221 is not a training decision.

Try the calculator

Use our free 1-Rep Max Calculator to get instant estimates from all four formulas. Enter your weight, reps, and optional RPE, and it handles the rest, including the deadlift correction and confidence bands.

Key takeaways

Test with 1 to 5 reps for estimates you can trust; accuracy falls off fast past 10 reps.
Multiply deadlift estimates by 1.10. Every formula lowballs the pull.
Use RPE to account for reps left in the tank and sharpen the estimate.
Program off a training max at 85 to 90 percent of your estimated 1RM, not the raw number.
Retest every 4 to 6 weeks as you get stronger. The estimate is a snapshot, not a tattoo.