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1:87 is the scale ratio, which means that a linear measurement of 1 actual unit is equal to 87 times the scale measurement. For example, one real foot equals 87 scale HO feet. But the ratio works for any linear unit of measurement, whether it's inches, meters, millimeters, miles, furlongs, or light-years. (an HO scale light-year is 67.5 billion actual miles long, by the way )

If you're asking how many actual inches are in a scale HO foot, then a little math is involved:

In 1 real foot (ft), there are 87 HO scale ft (HOft).

There are 12 real inches (in) in 1 real foot (ft).

So you multiply 1/87 (ft/HOft) x 12/1 (in/ft), and you get a ratio of 12/87, which equals 0.1379. The "ft" units cancel out, leaving you with inches / HO scale feet. 0.1379 comes out to just shy of 9/64 inches (per scale HO foot).

Hope that helps.

If you're asking how many actual inches are in a scale HO foot, then a little math is involved:

In 1 real foot (ft), there are 87 HO scale ft (HOft).

There are 12 real inches (in) in 1 real foot (ft).

So you multiply 1/87 (ft/HOft) x 12/1 (in/ft), and you get a ratio of 12/87, which equals 0.1379. The "ft" units cancel out, leaving you with inches / HO scale feet. 0.1379 comes out to just shy of 9/64 inches (per scale HO foot).

Hope that helps.

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I would suggest getting an HO Scale Ruler. Mascot made a nice one that was affordable in stainless steel. Mine has HO scale feet, along with S, O, and N. There is also drill & tap information and a metric scale. Since getting into detailing locomotives years ago, the scale ruler has become an important tool on my bench. http://www.walthers.com/exec/search?quick=scale+ruler

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