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.
- 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.
- 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.
- 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.
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||
||<0.8% at >30% body fat|
|41—45||y = -0.0172 x2 + 1.37 x + 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