Epley vs Brzycki: Which 1RM Formula Should You Use?

Published 25 October 2026 · 7 min read

Epley and Brzycki are the two formulas most one-rep-max calculators are built on. They take the same inputs — a weight and the reps you completed with it — and turn them into an estimated 1RM. Their answers match closely at low rep counts and drift apart as reps climb, so knowing where they agree (and why) helps you use both sensibly.

The two formulas, side by side

Both formulas estimate the weight you could lift for one repetition from a set performed at a higher rep count. Epley was published in 1985 from bench press testing, and Brzycki followed in 1993 as a refinement. The equations look different, but they describe the same idea: each additional rep you can perform represents a predictable slice of your max.

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Notice that Epley scales up linearly with reps, while Brzycki scales up as a fraction that grows steeply as reps approach 37 — which is why Brzycki is only used well below that point. In practice, both are applied to sets of 1 to 10 reps, and most calculators cap inputs somewhere in that range.

A worked example: 100 kg × 5

Say you bench pressed 100 kg for five clean reps. Epley estimates 100 × (1 + 5⁄30) = 116.7 kg. Brzycki estimates 100 × 36⁄(37 − 5) = 112.5 kg. The spread is about 4 kg, or roughly 4%. At three reps the gap shrinks to under 2%, and at ten reps it widens past 10%. That pattern — tight agreement at low reps, widening divergence as reps climb — is the single most useful thing to understand about these two equations.

Where they agree and where they drift

The table below shows both estimates for sets with 100 kg, rounded to the nearest tenth. Look at how the two columns stay close through the low reps and then separate.

A set at one rep is not an estimate at all — it is your 1RM, and both formulas correctly return the input unchanged. The further you move from that, the more the formula's assumptions matter, and the more the two equations disagree about what "five reps from failure" implies.

Why the drift happens

Epley assumes each extra rep adds exactly 1/30th of the lifted weight to your max. Brzycki assumes the relationship is curved, with your estimated max rising more slowly as reps increase. Real lifters sit somewhere between the two lines, and where exactly depends on the lift, their muscle fiber mix, training history, and how honestly the set was taken to near-failure. Neither equation is wrong; they are two different maps of the same territory.

Which one is more accurate?

Validation studies comparing formula predictions against directly tested maxes generally find a few consistent patterns. First, accuracy is best at low rep counts: estimates from sets of two to five reps land far closer to tested maxes than estimates drawn from sets of ten or more. Second, accuracy varies by exercise — a formula calibrated on bench press data tends to fit bench press better than squats or leg presses. Third, trained and untrained lifters can produce systematically different errors on the same formula.

Comparisons of Epley and Brzycki specifically tend to show Brzycki running slightly conservative (lower) at moderate rep counts, with Epley running higher. Some studies find Brzycki a touch more accurate for higher-rep sets; others find Epley better at low ones. The honest summary: at five reps or fewer, both are good, and the average of the two is at least as good as either.

How to choose one in practice

Pick one and stay consistent

For tracking progress, consistency matters more than which formula you pick. If you estimate 120 kg this month and 126 kg next month on the same equation, the change is real information. If you switch formulas between measurements, you cannot tell training progress from formula drift.

Use low-rep sets for the estimate itself

Whatever formula you choose, feed it honest, near-limit sets of five reps or fewer. A true five-rep max gives a dependable estimate; a set of twelve where you had four reps left in the tank gives neither formula anything useful to work with.

Consider averaging when reps creep up

If your program has you testing strength with sets in the six-to-eight range, taking the midpoint of Epley and Brzycki is a reasonable hedge, since real performance tends to fall between them. Our calculator's consensus view does this for you across all seven formulas.

Common questions

Which formula do most calculators use?

Epley is the most common default because it is the simplest to compute by hand, but any well-built calculator — including ours — lets you choose or compare several. Check which formula a chart or app is using before comparing its numbers to your log.

What about the other formulas?

Lombardi, O'Conner, Wathan, and Lander all answer the same question with slightly different curves. They cluster with Epley and Brzycki at low reps and spread out at high ones. Our accuracy guide compares all seven at each rep count.

Does rounding matter?

Only cosmetically. The formulas' precision is far coarser than a decimal point — treat estimates as ranges, and round to the nearest plate-friendly increment when you move them into your log.

Conclusion: two good answers to one question

Epley and Brzycki agree closely at the rep counts where estimates are most trustworthy, and drift apart exactly where estimates become shaky. Use either — or both — with hard sets of five reps or fewer, keep your method consistent over time, and treat the output as a planning number rather than a promise.

Related articles

• The Epley Formula Explained

  Worked examples and training applications for the most widely used 1RM equation.

• How to Calculate Your 1RM

  A step-by-step walkthrough from choosing a set to setting training loads.

• How Accurate Are 1RM Calculators?

  What the research says about formula accuracy at every rep count.