4 ms·

I generally just multiply miles * 1.5 for a rough approximation.

• FartyMcFarter 7y ago
  Adding 10% of the original number to that is often easy as well, and makes the estimate very close to the correct conversion.
  • hestipod 7y ago
    Works great for kg/lb conversions too. kg x2 + 10% = lbs lbs /2 - 10% = kg I've yet to find a fast one for C to F temp conversions though. It takes a bit longer to do the 9/5-5/9 + or - equation in your head.