TolpuddleSartre:
Multiply micros() by 62.5
That is weird math !!
If the OP wants to measure nanoseconds, I guess that's because he needs a precision of a few nanoseconds.
With AVR arduinos clocked at 16MHz, you can't expect this precision. With an arduino DUE clocked at 84 MHz, the best you can expect is a 12 ns precision. Therefore the question is : what sort of nanoseconds precision are you looking for ?