How to convert microns to gauge thickness

Written by pearl lewis
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How to convert microns to gauge thickness
Metal and plastic sheets are categorised by gauge number. (is sharp of metal image by Victor M. from

Whether you are purchasing trash bags for the garage, tin foil for the kitchen or sheet metal for your business, it is essential to buy the product with the right properties to get the job done. The properties of the product are determined by the material thickness. Manufacturers often report the thickness of their product in the form of a gauge number, which depends on the material type, rather than using the more common linear units. Converting material thickness to the industry equivalent gauge number ensures that the correct product is purchased.

Skill level:

Things you need

  • Calculator
  • Screw micrometer

Show MoreHide


    Measuring in Micron

  1. 1

    Identify the material--e.g., plastic or metal--for which the film thickness conversion is required.

  2. 2

    Classify the metal type as steel, galvanised steel, stainless steel, aluminium, copper or the appropriate alloy. Plastic need not be categorised, as gauge number scales are the same for all plastic types.

  3. 3

    Take a minimum of three thickness measurements at various points on the material sheet, using the screw micrometer, and calculate the average thickness. Report the thickness in micron.

    For Plastics

  1. 1

    Multiply the plastic film thickness measured in micron by the conversion factor 3.937.

    How to convert microns to gauge thickness
    Plastic bags with higher gauge numbers are thicker. (poubelles image by ninice64 from
  2. 2

    Round the result to three decimal places.

  3. 3

    Report the result as a number followed by the word "gauge" to differentiate it from other commonly used units.

    For Metals

  1. 1

    Convert the micron measurement to inches, as most sheet metal gauge tables only correlate thickness measurements given in inches with gauge numbers. Multiply the micron measurement by 3.937E-05 to obtain the equivalent measurement in inches.

    How to convert microns to gauge thickness
    Metric micron measurements are changed to inches. (Calculator image by Alhazm Salemi from
  2. 2

    Consult the Gauge and Weight Chart for Metals provided by the Engineering Toolbox or an equivalent gauge chart and isolate the sheet thickness column associated with the relevant metal--e.g., galvanised steel or aluminium. Gauge numbers for metals are based on the weight or density of the sheet metal, so the same gauge number refers to different thicknesses for different alloys or metal types.

  3. 3

    Find the value in the table which is closest in magnitude to the thickness--in inches--requiring conversion, and read off the equivalent gauge thickness.

Tips and warnings

  • An increase in the thickness for metal films is indicated by a decrease in the gauge number.
  • An increase in the thickness of plastic films is indicated by an increase in the gauge number.
  • If the calculator does not have an exponent function, enter the value 3.937E-05 as 0.00003937.

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