Health & Fitness

One Rep Max Calculator

Estimates your one-rep max from a weight lifted and the number of reps using two formulas, Epley and Brzycki, each shown to one decimal in your entered weight unit.

What this calculator does

The One Rep Max Calculator estimates your result instantly from the values you enter, using standard health & fitness formulas. Estimates your one-rep max from a weight lifted and the number of reps using two formulas, Epley and Brzycki, each shown to one decimal in your entered weight unit. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.

One Rep Max Calculator

Result

—
1RM (Epley)
—
1RM (Brzycki)

About One Rep Max Calculator

The One Rep Max Calculator estimates the most you could lift for a single rep from a submaximal set. It applies two well-known formulas at once: Epley (weight x (1 + reps/30)) and Brzycki (weight x 36 / (37 - reps)), each shown to one decimal in the weight unit you enter.

Formula & Mathematical Calculation

1RM (Epley) = f(Weight Lifted, Repetitions)

Calculated according to standard health formulas implemented in the calculator core.

Calculation Example

For 100 weight lifted for 5 reps: Epley = 100 x (1 + 5/30) = 116.7, Brzycki = 100 x 36 / (37 - 5) = 112.5. The tool shows 1RM (Epley) = 116.7 and 1RM (Brzycki) = 112.5.

Key Benefits

  • Gives two independent 1RM estimates, Epley and Brzycki, side by side
  • Works from a single submaximal set of weight and reps
  • Reports each estimate to one decimal in your chosen weight unit

How to Use this Calculator

  1. Enter weight lifted
    Type the weight you lifted into the Weight Lifted field (for example 100).
  2. Enter repetitions
    Type the number of reps completed (at least 1) into the Repetitions field (for example 5).
  3. Calculate
    Click Calculate and read the 1RM (Epley) and 1RM (Brzycki) result boxes.

Assumptions & Limitations

What the calculation assumes

  • Every value you enter is treated as an exact, known amount.
  • Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
  • Results use standard published formulas and account only for the values entered above.
  • Rounding is applied for display; the underlying calculation uses your full precision.
  • Results are returned in the same units you enter, unless the tool states the output unit.

What it does not cover

  • One Rep Max Calculator produces a calculated result for reference and learning, not a certified or official measurement.
  • Real-world outcomes differ when tolerances, rounding rules or local standards apply.
  • Definitions and standards vary by region and change over time; verify the convention that applies to your case.
  • Figures are only as accurate as the inputs you supply — check them before acting on the result.
  • For work where the result carries real consequences, confirm it against an authoritative source.

Frequently Asked Questions

Two: Epley, weight x (1 + reps/30), and Brzycki, weight x 36 / (37 - reps). Both are shown so you can compare.

They are different regression formulas. For 100 at 5 reps, Epley gives 116.7 and Brzycki gives 112.5; the gap tends to widen at higher rep counts.

No. The tool is unit-agnostic; enter kg or pounds and both estimates come back in that same unit.

Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.