Obligatory repeat of the fact that the ratio between miles and kilometres is ln(5), correct to less than 0.01% (yes, that's a percent of a percent).

The golden ratio or Fibonacci numbers are used more often for the same trick but they're off by, at best, very slightly worse than 0.5%.

Thanks, I hate it

Knot is just nautical mile per hour, so it can be simplified so:

π miles = e nautical miles

God french fry filching dammit.