What is a one-rep max (1RM)?

A one-rep max is the maximum weight you can lift for a single complete repetition of an exercise with good form. It is the standard measure of absolute strength in resistance training.

Which formula is most accurate?

No single formula is universally best — accuracy varies by individual, exercise, and rep range. Brzycki and Epley are most widely cited. Averaging all five formulas generally gives a more reliable estimate than relying on any one alone.

Why is the calculator limited to 12 reps?

Beyond 12 repetitions, 1RM prediction accuracy drops sharply because rep-max formulas assume a near-maximal effort. Sets of 15+ reps involve more muscular endurance than pure strength, making extrapolation unreliable.

Should I actually attempt my calculated 1RM?

Not necessarily. Estimated 1RMs are most valuable for setting training loads at various percentages. Actual maximal attempts carry injury risk and should only be done with proper warm-up, a spotter, and experience.

What do the training percentages mean?

Different percentage zones target different adaptations. 50–60% builds technique and endurance; 70–80% develops hypertrophy and general strength; 85–95% trains maximal strength and neural drive.

1RM Calculator

Name: 1RM Calculator
Availability: InStock
Author: Nham Vu

Enter the weight you lifted and how many reps you performed (1–12) to instantly see your estimated one-rep max and a full training percentage breakdown.

Lift Details

Weight Lifted

Reps Performed

Formula

Enter a weight and rep count, then click Calculate.

Supports 1–12 reps using 5 validated formulas.

Average 1RM

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Formula Breakdown

Formula	Est. 1RM

Training Percentage Table

% of 1RM	Weight	Zone

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Summary

Enter the weight you lifted and how many reps you performed (1–12) to instantly see your estimated one-rep max and a full training percentage breakdown.

How it works

Enter the weight you lifted in the Weight field.
Select your unit — pounds (lb) or kilograms (kg).
Enter the number of reps you performed (1 through 12).
Choose a specific formula or leave it on "Average all 5" for a consensus estimate.
Click Calculate to see your estimated 1RM and the full training percentage table.

Use cases

Determine your theoretical maximum lift for programming a strength cycle.
Set target weights for each percentage zone in a powerlifting or Olympic lifting program.
Track relative strength progress over time without maxing out every session.
Compare your estimated 1RM across different formulas for a more confident number.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu