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One Rep Max Calculator

Use this one rep max calculator to review an educational health calculation for one rep max.

Primary answer
Estimated 1RM
Inputs to verify
Weight lifted, Weight unit, and Repetitions
Use type
Use as an estimate that depends on assumptions.
Keyword intent
one rep max calculator

Calculator

One Rep Max Calculator

Calculates estimated 1rm from weight lifted, weight unit, repetitions. Defaults are filled in so you can review a working example before changing inputs.

Enter the load lifted in the selected unit.

Choose kilograms or pounds. The estimate uses the same unit.

reps

Whole-number repetitions from 1 to 12.

Result

Result reflects the current submitted inputs.

  • Risk B
  • Reviewed 2026-05-26
  • 3 sources
Estimated 1RM112.5
Input load as percent of estimate88.89%
Formula usedBrzycki (1993): 1RM = weight * 36 / (37 - reps)
Safety noteEstimated 1RM is not medical, coaching, or training-load advice; actual max depends on lift, technique, fatigue, equipment, and supervision.

Breakdown

Weight unit
kg
Repetitions
5 reps
  • The output is an estimate, not a measured one-repetition maximum.
  • The weight unit is preserved; kg inputs return kg estimates and lb inputs return lb estimates.
  • The formula is limited to integer repetitions from 1 to 12 in this MVP.
  • Actual maximal performance can vary by lift, technique, fatigue, equipment, and supervision.
  • This calculator is not medical, coaching, or training-load advice.

Accuracy notes

Risk level
B
Reviewed
2026-05-26
Sources
3
Primary result
Estimated 1RM

Formula logic is kept in a pure calculator module with fixtures, source notes, and page-visible assumptions.

Categories

What the result means

Estimated 1RM is the number to carry forward from this one rep max calculation. Estimated one-repetition maximum in the same unit as the input weight. Treat the result as educational context, then read the limitations and assumptions before discussing it with a professional. Use input load as percent of estimate, formula used, and safety note to explain why estimated 1RM moved when an input changed. Record the inputs you used and verify any health concern with a qualified professional.

Estimated 1RMEstimated one-repetition maximum in the same unit as the input weight.
Input load as percent of estimateHow the entered set weight compares with the estimated 1RM.
Formula usedFormula label shown with the result.
Safety noteVisible caveat that the result is not medical, coaching, or training-load advice.

Use the result this way

  1. Start with Estimated 1RM, then use supporting outputs only to explain the primary answer.
  2. Verify weight lifted, weight unit, and repetitions before copying the result.
  3. Choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges.
  4. Record the inputs you used and verify any health concern with a qualified professional.

User job

How to use this calculator

Use One Rep Max Calculator when you need estimated 1rm, then use input load as percent of estimate and formula used to check the context for general wellness education and preparing for a professional conversation.

Best for

  • Understanding a formula-based estimate
  • Seeing which inputs drive a health-related output
  • Reviewing a default example before entering your own weight lifted and weight unit.

Check before relying

  • Health formulas can be population-specific; do not use the result as diagnosis or treatment advice.
  • The output is an estimate, not a measured one-repetition maximum.
  • The weight unit is preserved; kg inputs return kg estimates and lb inputs return lb estimates.
  • Source context: Journal of Physical Education, Recreation & Dance, reviewed 2026-05-26.

Next useful step

  • Target Heart Rate CalculatorUse next when the fitness task needs age-predicted maximum heart rate instead of estimated 1RM.
  • BMR CalculatorUse next when you need estimated BMR from age and sex used by equation after checking estimated 1RM.
  • Body Fat CalculatorUse next when you need estimated body fat from age and sex used by equation after checking estimated 1RM.

Formula

Estimated 1RM uses the Brzycki equation: weight * 36 / (37 - repetitions). Key assumptions: The output is an estimate, not a measured one-repetition maximum. The weight unit is preserved; kg inputs return kg estimates and lb inputs return lb estimates. The formula is limited to integer repetitions from 1 to 12 in this MVP.

  • Estimated 1RM uses the Brzycki equation: weight * 36 / (37 - repetitions).
  • The output is an estimate, not a measured one-repetition maximum.
  • The weight unit is preserved; kg inputs return kg estimates and lb inputs return lb estimates.
  • Primary source context: Journal of Physical Education, Recreation & Dance.

Inputs

Enter weight lifted, weight unit, and repetitions for general wellness education and preparation for a professional conversation. Before calculating, choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges. Weight lifted: Enter the load lifted in the selected unit. Weight unit: Choose kilograms or pounds. The estimate uses the same unit. Repetitions: Whole-number repetitions from 1 to 12.

Weight liftedEnter the load lifted in the selected unit.
Weight unitChoose kilograms or pounds. The estimate uses the same unit.
RepetitionsWhole-number repetitions from 1 to 12.

Example

Using the default inputs, One Rep Max Calculator returns estimated 1RM of 112.5. Adjust weight lifted, weight unit, and repetitions to match your own scenario.

FAQ

How is estimated 1RM calculated here?

Estimated 1RM uses the Brzycki equation: weight * 36 / (37 - repetitions). The first assumption to check is: The output is an estimate, not a measured one-repetition maximum.

What does Estimated 1RM mean for one rep max?

Treat the result as educational context, then read the limitations and assumptions before discussing it with a professional. Secondary values such as input load as percent of estimate, formula used, and safety note are there to explain the primary answer, not to replace it.

What should I enter for Weight lifted?

Enter the load lifted in the selected unit. Choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges.

How does Weight unit change estimated 1RM?

Choose kilograms or pounds. The estimate uses the same unit. Changing it can alter estimated 1RM because the formula uses the submitted inputs together. Also compare measurement method, formula population, age range, units, sex or activity assumptions, and clinical context.

Why does the one rep max example show 112.5 for estimated 1RM?

The default inputs produce 112.5 for estimated 1RM. Treat that as a format and scale check, then replace every default value with your own inputs.

Can the one rep max result diagnose or prescribe anything?

No. Use it as educational context only. Health formulas can depend on population, measurement method, age range, and clinical context.

Sources

Last reviewed: 2026-05-26

  • Reviewed 2026-05-26 · Source 1993
    Strength Testing - Predicting a One-Rep Max from Reps-to-FatigueJournal of Physical Education, Recreation & Dance. Primary source citation for estimating one-rep max from weight lifted and repetitions to fatigue.
    Scope
    Original Brzycki one-repetition maximum prediction article.
    Supports
    Primary source citation for estimating one-rep max from weight lifted and repetitions to fatigue.
  • Reviewed 2026-05-26 · Source 1997-11
    The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and DeadliftJournal of Strength and Conditioning Research. B-risk limitation note that prediction equations can correlate strongly with measured 1RM while still differing by exercise and population.
    Scope
    Peer-reviewed comparison of one-repetition-maximum prediction equations across bench press, squat, and deadlift.
    Supports
    B-risk limitation note that prediction equations can correlate strongly with measured 1RM while still differing by exercise and population.
  • Reviewed 2026-05-26 · Source 2012
    Training Load ChartNational Strength and Conditioning Association. Independent comparison point for fixture verification, including the chart example that 160 lb for 8 reps estimates about 200 lb 1RM.
    Scope
    Training load chart adapted from maximum-based-on-reps tables.
    Supports
    Independent comparison point for fixture verification, including the chart example that 160 lb for 8 reps estimates about 200 lb 1RM.

Disclaimer

This health calculator is for educational estimates only. It does not diagnose, treat, or replace advice from a qualified health professional.