1RM Formula Comparison — Epley vs Brzycki vs Lander

How 1 Rep Max Is Estimated

Your one-rep max (1RM) is the maximum weight you can lift for a single complete repetition of an exercise with proper form. Testing your true 1RM carries a meaningful injury risk — especially for compound lifts like the bench press, squat, and deadlift — so several validated formulas estimate it from a submaximal effort of multiple reps. This calculator uses three well-established formulas and provides their average, which is more reliable than any single formula alone.

Each formula was derived from regression analysis of actual lifting data, and they agree reasonably well in the 3–10 rep range. As the number of reps increases, the formulas diverge and accuracy decreases. For the best estimate, use a weight you can lift for 3–8 reps with good form.

The Formulas

Worked Example

If you bench press 80 kg for 8 reps, your estimated 1RM by each formula is: Epley = 80 × (1 + 8/30) = 101 kg, Brzycki = 80 × (36/29) = 99 kg, Lander = 80 × (100/79.93) = 100 kg. The average of the three formulas is (101 + 99 + 100) ÷ 3 ≈ 100 kg. This is the number you would use for programming training percentages. If you used a weight of 80 kg for only 5 reps, the same formulas would estimate a 1RM of approximately 93 kg — lower because the 5-rep set represents a smaller fraction of your true maximum.

FAQ-Style Explanations

Which formula is most accurate? The Epley and Brzycki formulas are both well-validated. Epley tends to be slightly more accurate for higher rep ranges (8+), while Brzycki works better for lower reps (under 8). The average of all three is the most reliable single estimate.

How many reps should I use for the estimate? For the most accurate result, use a weight you can lift for 3–10 reps with good form but not more — the formulas lose accuracy beyond 12 reps because muscular endurance, not strength, becomes the limiting factor.

Can I use these formulas for any exercise? They work best for compound lifts (bench press, squat, deadlift, overhead press). For isolation exercises, the formulas may overestimate slightly because smaller muscle groups fatigue more quickly.

Known Limitations

• The formulas are derived from specific populations and may be less accurate for very experienced lifters, beginners, or individuals with a very high proportion of fast-twitch muscle fibers.
• All formulas assume the set is performed to failure (or very close to it). If you stop several reps short of failure, the estimate will be inflated.
• The 1RM estimate is exercise-specific. Your bench press 1RM has no relationship to your squat or deadlift 1RM — each must be calculated separately.

The Three Major 1RM Formulas Side by Side

All three formulas take two inputs — the weight lifted and the number of clean reps — and output an estimated one-rep max. The Epley formula (1985) is the most widely used and is built into most gym apps. The Brzycki formula (1993) is derived from powerlifting data and is considered the most accurate across a wide rep range. The Lander formula is the simplest and the most conservative. Below are the three equations and how they behave across the rep spectrum.

• Epley: 1RM = Weight × (1 + Reps / 30). Example at 80 kg × 5 reps = 93.3 kg. Widely used; overestimates at high reps.
• Brzycki: 1RM = Weight / (1.0278 − 0.0278 × Reps). Same inputs = 93.0 kg. Most accurate overall.
• Lander: 1RM = Weight + (Weight × Reps / 30). Same inputs = 93.3 kg. Simplest; most conservative.
• Wathan (4th option): 1RM = 100 × Weight / (101.3 − 2.67123 × Reps). Rarely used but appears in academic studies.

Divergence at High Reps (12+)

At low rep counts (1–6), all three formulas produce results within 1 to 2 percent of each other, so the choice of formula has little practical impact. The divergence becomes meaningful at rep counts of 10 or more, and especially at 12–15+ reps. At 12 reps with 50 kg, Epley estimates roughly 69 kg, Brzycki roughly 65 kg, and Lander roughly 70 kg — a spread of about 7 percent. This matters because many hypertrophy programs use rep ranges of 8–12, and a 5–7% error in the estimated 1RM can push your training percentages too high (risking failure mid-set) or too low (wasting effort). Most researchers recommend using the Brzycki formula or an Epley estimate capped at 8–10 reps for this reason.

Epley Overestimates, Lander Underestimates

Controlled studies comparing formula output to actual 1RM tests consistently show that the Epley formula tends to overestimate true max, particularly at rep counts above 6, while the Lander formula tends to underestimate. The Brzycki formula sits closest to measured values across the widest rep range. The practical implication is straightforward: if you use Epley for a 10-rep set, your calculated 1RM will probably be slightly higher than your true max, and training at 85% of that number may actually be closer to 87–88% — a modest but meaningful jump. Lander is the safer bet when you want to be certain you are not overloading.

• Epley bias: overestimates true 1RM by roughly 1–5% depending on rep count, with bias increasing above 8 reps.
• Brzycki bias: closest to measured values; deviation typically under 2%.
• Lander bias: underestimates true 1RM; the safest choice for heavy programming.

Recommended Usage Per Rep Range

The best practice is to use a rep range that produces an accurate estimate (3–6 reps) and to use a single formula consistently so your progress can be compared over time. If you already have a training program built around one formula, stick with it rather than switching formulas mid-cycle. Below are practical recommendations by rep range and training goal.

• 1–3 reps: any formula is fine; the estimate is essentially your actual max.
• 3–6 reps: the sweet spot for all formulas. Brzycki is recommended for maximum accuracy.
• 6–10 reps: Brzycki or Epley. Treat the result as an estimate, not a precise number.
• 10+ reps: avoid using formulas to estimate 1RM. Use a direct test or RPE-based programming instead.