What is the one rep max (1RM)?

The one rep max (1RM) is the maximum weight you can lift for exactly one repetition with clean technique. It is the key metric in strength training and the basis for percentage-based programs like 5/3/1.

Which 1RM formula is the most accurate?

For 2–10 reps, all four formulas (Epley, Brzycki, Lander, Lombardi) are similarly accurate. Brzycki is considered especially precise at 6–10 reps, Epley at lower rep counts.

How do I calculate my 1RM without a max attempt?

Simply enter a working weight and the reps you completed into the calculator. The formulas estimate your 1RM from the weight-to-reps ratio — most accurate at 2–10 reps.

All Tools

Tools

How much can you lift for one rep?

Enter your weight and reps — the calculator estimates your One Rep Max using four scientific formulas.

Unit:

Weight lifted

Reps completed

Most accurate for 2-10 reps

Percentage table

Based on your estimated 1RM

% of 1RM	approx. Reps	Weight
100%	1	—
95%	2	—
90%	3-4	—
85%	5-6	—
80%	7-8	—
75%	9-10	—
70%	11-12	—
65%	13-15	—
60%	16-20	—

What is One Rep Max (1RM)?

The One Rep Max (1RM) is the maximum weight you can lift for exactly one repetition with proper form. It's the most important metric in strength training — the foundation for percentage-based programs like 5/3/1, Smolov, or GZCLP.

Direct 1RM testing is effective but risky and fatiguing. That's why most formulas use your working weight and reps to estimate the 1RM. The formulas are most accurate for 2-10 repetitions. Above 10 reps, estimation error increases significantly — Epley and Brzycki can diverge by 5-10%.

The four formulas implemented here — Epley (1985), Brzycki (1993), Lander, and Lombardi — each use slightly different mathematical models. Brzycki is generally considered more accurate at 6-10 reps, while Epley tends to be better at lower rep ranges. For practical purposes, averaging multiple formulas gives the most reliable estimate.

Your estimated 1RM is not a number you should actually attempt in the gym. It's a planning tool — use it to calculate Training Max percentages, set volume targets, and track strength progression over time. A 5 kg increase in your estimated 1RM over 8 weeks is a concrete, measurable sign of progress.

The four formulas compared

Epley

Epley (1985) — The most widely used formula. Slightly conservative at low reps, good for 3-10 repetitions.

Brzycki

Brzycki (1993) — Considered more accurate at 6-10 reps. Preferred by many strength coaches.

Lander

Lander — Compromise between Epley and Brzycki. Good all-around formula.

Lombardi

Lombardi — Simplest formula, tends to give conservative estimates at high reps.

Sources

Epley B (1985). Poundage Chart. Boyd Epley Workout.
Brzycki M (1993). Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue. JOPERD, 64(1):88-90.
LeSuer DA et al. (1997). The Accuracy of Prediction Equations for Estimating 1-RM Performance. JSCR, 11(4):211-213.