Body fat formulas for your AccuMeasure body fat calipers

by Rudd-O published 2017/01/18 15:41:00 GMT+0, last modified 2017-01-18T15:50:29+00:00
This is a set of formulas that you can use to convert the measurements of your AccuMeasure calipers to body fat percentage. Follow the instructions, then plug the number on the appropriate formula. You'll get quite the accurate measurement of your body fat, with none of the hassle of looking up numbers on a table.

The x in the formulas represent what you measured with your AccuMeasure in millimeters, when you follow the instructions correctly, and they are derived from the table that ships with the device.  Plug the measurement (fractional values are okay) into the formulas.  The output of the formula is a percentage number (as in 0—100, not 0—1).  The maximum error (discrepancy) between these formulas and the values in the AccuMeasure table is documented in the tables below.


  1. Use these formulas on your favorite spreadsheet to track your body fat daily.  That way you don't have to do math or look stuff up.  The example spreadsheet formula is next to the mathematical one in the tables below.
  2. Always measure yourself right after you wake up.  Never change the time you measure relative to when you wake up — you'll get erratic measurements.
  3. Always measure in exactly the same way you did the previous day.  Pinch the same abdominal area, clip the same fold.  Day-to-day repeatability of the measurements is more important than absolute accuracy.

Men's formulas

Age bracket Mathematical
x is mm, y is body fat %
Excel / LibreOffice / spreadsheet
A1 is cell containing mm, output is body fat %
Maximum margin of error
36—40 y = -0.0172 x2 + 1.372 x + 2.28 =-0.0172 * (A1 * A1) + 1.372 * A1 + 2.28 <0.8% at >30% body fat
41—45 y = -0.0172 x2 + 1.37 x + 3.4
=-0.0172 * (A1 * A1) + 1.37  * A1 + 3.4 <1.8% at ~25% body fat

LibreOffice macro formula for your spreadsheet

Function bodyfat(measuremm As String, age As String)
	Dim measuremm_d as Double
	Dim age_d as Double

	measuremm_d = Val(measuremm)
	age_d = Val(age)

	If age_d >= 36 and age_d <= 40 Then
		bodyfat = (-0.0172 * (measuremm_d * measuremm_d)) + (1.372 * measuremm_d) + 2.28
	Elseif age_d >= 41 and age_d <= 45 Then
		bodyfat = (-0.0172 * (measuremm_d * measuremm_d)) + (1.37 * measuremm_d) + 3.4
	End If
End Function