📊 One-Rep Max Calculator

How the one-rep max formulas work

A one-rep max (1RM) is the most weight you can lift for a single clean repetition. Rather than grinding out a true max attempt every time — which is fatiguing and carries injury risk — you can estimate it from a lighter set taken close to failure. This calculator runs three of the most widely used equations and averages them:

• Brzycki: weight × (36 / (37 − reps)). Tends to be conservative and is most reliable at 1–6 reps.
• Epley: weight × (1 + reps / 30). A long-standing standard that holds up well at low-to-moderate reps.
• Lander: (100 × weight) / (101.3 − 2.67123 × reps). Useful across a wider range of reps.

Getting the most accurate estimate

Use a set you took within a rep or two of failure, ideally in the 3–6 rep range. The further past ~10 reps you go, the more the estimate drifts, because high-rep performance depends heavily on conditioning and pain tolerance rather than pure maximal strength. Once you have a number, you can use it to set training percentages — then see how it stacks up on the strength standards calculator.

Worked example

Say you bench-pressed 185 lb for 8 reps. Plugging that in: Brzycki returns about 230 lb, Epley about 234 lb, and Lander about 231 lb — averaging to roughly 232 lb as your estimated one-rep max. You'd then train your working sets as percentages of that number (for example, 5 sets of 3 at ~85%, or about 197 lb).

Accuracy and limitations

• Most reliable at 1–6 reps; beyond ~10 reps the estimates inflate because high-rep performance depends on conditioning and pain tolerance, not just maximal strength.
• It's an estimate, not a guarantee — never load a barbell to a calculated max without proper warm-ups, a spotter, and good technique.
• Results differ by lift; a number derived from bench won't transfer directly to squat or deadlift.

Sources & references

The three formulas come from the strength-and-conditioning literature: Brzycki, M. (1993), "Strength testing: predicting a one-rep max from reps to fatigue"; Epley, B. (1985), Boyd Epley Workout; and Lander, J. (1985), "Maximums based on reps." They remain standard methods for estimating 1RM from submaximal sets.