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Anyone know of a good scale inch calculator?


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An inch contains 25.4 millimeters. It is almost a one to twenty-five ratio! One MM equals one 1/25 scale inch!

You may want to use a pocket calculator or the calculator on your computer for longer dimensions where the .4 comes into play like wheelbases. If you have a 120 inch wheelbase you would multiply by 25.4 and then divide by 25 to get your scale wheelbase in mm.

120" X 25.4 = 3048

3048 divided by 25 = 121.92mm

That is about 2 mm longer than if you used a one to one ratio.

I hope that helps.

Edited by Modelmartin
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For 1/25 scale, all you need to remember is that 1 mm = 1 scale inch.

Any fractional difference is way too small to ever be noticed.

I agree. I used 6mm Tamiya masking tape to mark a chop on a Monogram model A coupe, and the reattached top looks just about dead-on for the 6" chop on my buddy's 1:1

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An inch contains 25.4 millimeters. It is almost a one to twenty-five ratio! One MM equals one 1/25 scale inch!

You may want to use a pocket calculator or the calculator on your computer for longer dimensions where the .4 comes into play like wheelbases. If you have a 120 inch wheelbase you would multiply by 25.4 and then divide by 25 to get your scale wheelbase in mm.

120" X 25.4 = 3048

3048 divided by 25 = 121.92mm

That is about 2 mm longer than if you used a one to one ratio.

I hope that helps.

Or, you could just multiply the measurement in inches by 1.016 to get the measurement in mm. 120 X 1.016 = 121.92. That eliminates a little wear and tear on the calculator keys. :)

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You could just multiply the measurement in inches by 1.5875 to get the measurement in mm. 120 X 1.5875 = 190.5. That eliminates a little wear and tear on the calculator keys. :)

If you take 25.4 and divide it by the scale, it will give you the conversion factor for real inches to mm in your scale. 25.4/25=1.016 (see previous example). 25.4/16=1.5875. Here's a list for common automotive scales:

8 - 3.175

12 - 2.1166

16 - 1.5875

20 - 1.27

24 - 1.0583

25 - 1.016

32 - 0.7937

43 - 0.5906

64 - 0.3968

The number in the right column is the length (in mm) of one scale inch. Multiply that by the full size measurement in inches, and you will have the size of your model part in mm. A 7" headlight in 1/16 scale will be 11.1125mm (7 X 1.5875); a 5-3/4" headlight will be 9.1281mm (5.75 X 1.5875).

Sorry to get so long-winded, but I hope that it will help someone.

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