Asked — Edited

Conversion Trick For Inches To Millimeters

This is for anyone out there who would like to know a metric to imperial conversion trick on a calculator. I only post this due to another thread where there was a lot of mixed measurements due to measuring device availability.

On a calculator with a tax- and tax+ button, set the tax as 2440. When you have a measurement in inches, hit the tax+ for millimeters, and tax- for millimeters to inches. ;)

We use this at work dealing with European hardware that are metric and the cabinets we make using imperial measurements.


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I thought the world was going to do away with the metric and imperial system and come over to the USA way of doing it? Come on, ya know ya really wanta do it? :P


Great trick, but shouldn't it be 2540? If I remember correctly, one inch is equal to 2.54 centimeters.


Niek is right... 2.54cm or about 25.4mm per inch...


@Neik and @RichardR, I know the direct multiplier for conversion (25.4), but 2440 is the number you set for the tax button. I'm not sure what the calculator does in the background to make this work (I'm not the one who found the number, one of our fresh from school engineers spent two hours trying out different combinations of numbers till it worked) but it works. I double checked it this morning.

I have also included the chart we use for conversions.

User-inserted image

@Dave Schulpius - WIKI - "The US government passed Omnibus Trade and Competitiveness Act of 1988, which made the metric system "the preferred system of weights and measures for US trade and commerce". The legislation states that the federal government has a responsibility to assist industry as it voluntarily converts to the metric system, i.e., metrification. This is most evident in US labeling requirements on food products, where SI units are almost always presented alongside customary units. According to the CIA Factbook, the US is one of three nations (the others being Liberia and Burma) that has not adopted the metric system as their official system of weights and measures.";) :P