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1RM Calculator

Estimate your 1RM from weight and reps using the existing strength calculator formulas.

Enter the weight successfully lifted for the rep set.

Use a whole number from 1 to 30. Lower-rep sets are usually more reliable.

Status: initial

Results

Awaiting calculation

Calculator guide

Introduction

Use this 1RM calculator to estimate a one rep max from a recent working set and compare training loads.

Purpose

Designed for quick strength estimates and training percentages; it is not a substitute for safe coaching or medical advice.

One-rep max method

The calculator supports common 1RM formulas such as Epley, Brzycki, Lombardi, O'Conner, and an average of those estimates.

Variable explanations

Weight lifted

The load successfully lifted for the full set.

Repetitions

The number of completed reps with proper range and control.

Weight unit

Choose pounds or kilograms. Results stay in the same unit.

Formula

The selected equation used to estimate one-rep max.

Training percentage

A suggested load based on a percentage of estimated 1RM.

Formula guide

Epley

1RM = weight x (1 + reps / 30)

  • Weight is the completed set load.
  • Reps are completed repetitions.

A common simple estimate for moderate rep ranges.

Brzycki

1RM = weight x 36 / (37 - reps)

  • Best used for rep counts below 30.

A classic one-rep max equation used in many calculators.

Lombardi

1RM = weight x reps ^ 0.10

  • Uses an exponent for rep adjustment.

Provides another perspective on rep-to-max conversion.

Worked examples

Bench press example

  1. Weight lifted: 225 lb.
  2. Repetitions: 5.
  3. Using Epley, estimated 1RM = 225 x (1 + 5 / 30) = 262.5 lb.

Kilogram example

  1. Weight lifted: 100 kg.
  2. Repetitions: 3.
  3. Using Epley, estimated 1RM = 110 kg.

Training percentage example

  1. If estimated 1RM is 200 lb, 80% is 160 lb.
  2. Training percentages help plan submaximal working sets.

Common mistakes

Treating an estimate as a guarantee

One-rep max formulas estimate strength and can be wrong for individual lifters.

Using very high rep sets

Higher rep counts tend to make 1RM estimates less reliable.

Ignoring technique

Only use reps completed with consistent range, control, and form.

Testing maxes too aggressively

Use conservative loading, proper warmups, and qualified supervision.

FAQs

What does this Strength Calculator do?
It estimates one-rep max from weight lifted and repetitions.
What is one-rep max?
One-rep max, or 1RM, is the estimated maximum weight for one repetition.
Which formula should I use?
Epley is a common default. Comparing formulas can show a reasonable estimate range.
Is the result exact?
No. It is an estimate and can vary by lifter, lift, technique, fatigue, and rep range.
Can I use kilograms?
Yes. Choose kilograms and the result will remain in kilograms.
Can I use pounds?
Yes. Choose pounds and the result will remain in pounds.
Why limit reps to 30?
Very high rep sets usually make one-rep max estimates less reliable.
What is the Epley formula?
Epley estimates 1RM as weight x (1 + reps / 30).
What is the Brzycki formula?
Brzycki estimates 1RM as weight x 36 / (37 - reps).
What is the Lombardi formula?
Lombardi estimates 1RM as weight x reps raised to the 0.10 power.
What is the O'Conner formula?
O'Conner estimates 1RM as weight x (1 + 0.025 x reps).
What are training percentages?
They are loads calculated from a percentage of estimated 1RM.
Can this calculator replace coaching?
No. It is an estimate for planning, not coaching, medical, or safety advice.
Should beginners test one-rep max?
Beginners should be cautious and use qualified coaching before max testing.
Why do different formulas give different results?
Each formula models fatigue and repetitions differently, so estimates naturally vary.

References

Related calculators

Last updated and version history

Last updated: 2026-07-10

  • 1.0.0 (2026-07-10): Added 1RM keyword variant backed by the strength calculator engine.