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Relative Strength Calculator

Work out relative strength instantly with clear inputs, formula shown and shareable results.

About Relative Strength Calculator

Relative strength divides the load by body weight, but simple division favours light lifters because muscle cross-section scales with the two-thirds power of mass rather than linearly. The allometric score, load divided by body weight to the power 0.667, corrects for that and is the fairer comparison across very different sizes.

Formulas

Relative strength

relative = load / body weight

Allometric scaling

score = load / body weight^0.667

Worked example

With the default values below, Relative Strength Calculator returns Relative Strength of 1.600. Change any input above and every figure here is recalculated in your browser.

Inputs used

Weight liftedminimum 0 kg
120 kg
Body weightminimum 0 kg
75 kg

Results

Relative Strength
1.600 x bodyweight
Allometrically Scaled Score
6.747
Lift As A Percentage Of Body Weight
160.0%
Assessment
Above average

Step by step

  1. 1Values used
  2. 2Relative strength
  3. 3Allometric scaling
  4. 4Relative Strength= 1.600 x bodyweight
  5. 5Allometrically Scaled Score= 6.747
  6. 6Lift As A Percentage Of Body Weight= 160.0
  7. 7Assessment= Above average

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.

Frequently Asked Questions

Why the two-thirds power?

Because strength depends on muscle cross-sectional area, which scales as the square of length while mass scales as the cube - giving an exponent of 2/3.

Which figure should I use?

Simple ratio for bodyweight movements like pull-ups, allometric scaling when comparing lifters of very different sizes.

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