Estimate your one-rep max (1RM) from any weight and rep count, using the Epley and Brzycki formulas — no need to attempt a true maximal lift.
A one-rep max, or 1RM, is the heaviest weight you can lift for a single complete repetition of an exercise with good form. It's a core reference number in strength training, used to set training percentages, track progress, and compare strength across lifters.
Testing a true 1RM means working up to a single maximal attempt, which carries real injury risk and requires several fatigue-free attempts to find the exact number. Most lifters instead estimate 1RM from a lighter set taken close to failure, typically in the 3–10 rep range.
This calculator provides general informational estimates and is not a substitute for professional coaching. Always use proper form and appropriate spotting when attempting heavy lifts.
Example 1: 100 kg for 5 reps — Epley: 100 × (1 + 5/30) = 116.7 kg. Brzycki: 100 × 36 / 32 = 112.5 kg. Average estimate: ~114.6 kg.
Example 2: 60 kg for 10 reps — Epley: 60 × (1 + 10/30) = 80 kg. Brzycki: 60 × 36 / 27 = 80 kg. Both formulas agree closely at this rep range.
| % of 1RM | Typical rep range | Common goal |
|---|---|---|
| 85–100% | 1–5 reps | Maximal strength |
| 70–85% | 5–8 reps | Strength / power |
| 60–75% | 8–12 reps | Hypertrophy (muscle growth) |
| <60% | 12+ reps | Muscular endurance |
What is a 1-rep max? A one-rep max (1RM) is the heaviest weight you can lift for a single complete repetition of an exercise with good form.
Why estimate 1RM instead of testing it directly? Testing a true 1RM carries injury risk and requires several fatigue-free attempts. Estimating from a lighter set close to failure is safer and still useful for programming training loads.
Which formula is more accurate, Epley or Brzycki? Neither is universally more accurate. Brzycki tends to track slightly better at lower rep counts (under about 10), while Epley is simpler and widely used. Averaging both gives a reasonable middle estimate.
How accurate is an estimated 1RM? Estimation formulas are reasonably accurate up to about 10-12 reps. Beyond that, endurance and fatigue start to influence the result more than raw strength, so accuracy drops.
How do I use 1RM to plan training loads? Training loads are commonly set as a percentage of estimated 1RM, such as 70-85% of 1RM for strength-focused work or 60-75% for hypertrophy-focused volume training.