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How to Convert Millimeters to HO Scale Feet

HO trains are model trains. They are half the size of O-scale trains, which is how they got their name: "HO" is an abbreviation of "Half O." The models are 1/87 the size of genuine trains. Everything in the HO setup must match in scale to complete the illusion of a miniature train chugging through a miniature landscape. There are converters available that can change any dimension to HO scale, but the process is simple to work out by hand.

Things You'll Need

Pencil
Paper

Instructions

- 1
  Divide 1 by 87. This gives you the decimal of the fraction of an inch. The decimal is 0.0114.
- 2
  Multiply the decimal scale of an inch by 12 to get the scale foot. This results in 0.138 of an inch is equal to a foot in HO scale.
- 3
  Multiply the scale foot by 25.4, which is the number of millimeters in a single inch. The answer is 3.5 millimeters equals a single HO scale foot.
- 4
  Multiply the number of HO feet by 3.5 to determine the number of millimeters of material you require.

Model Railroads