Photo: DJHSilver/Flickr

I have my own little trick I've used. Take a number like 50. Take half of 50 and add it. 50+25=75. Knock a digit off the original number, 50 becomes 5. Add that, 75+5=80. 50 miles = 80kms.

 

70miles=70+35+7=112kms

When I got stationed in Germany they taught us to convert kilometers to miles by multiplying by 6 and moving the decimal to the left one. To convert kilometers to miles you divide by 6 and move the decimal to the right one. It's quick and easy.

I just push the button on my dash and the magic numbers change.

A good way to do the kilometer/mile thing is the 3-5 method. It was taught to military folks going to Europe back in the 60's. Kilometers to miles: divide by 5, multiply times 3 Miles to Kilometers: divide by 3, multiply times 5

 

Of course it isn't precise, but this isn't about accuracy. It was meant to be a simple way you could convert "in your head" things like speed limits and distance. For an average American housewife, in Germany, this worked well enough.

Yes 160 kilometers is 100 miles so he ratio is 1.6 (although Fibonacci is 1.61...ish)

 

The easiest way to convert, though, is probably...

 

For miles to kilometers divide by 5 then multiply by 8. For kilometers to miles divide by 8 then multiply by 5.

To convert kilometer to miles you could just multiply k x .6 and add 1 for every 50k, e.g. 100k x .6 = 60 + 2 = 62m. Actual results 62.14.