Yes easy isnt it - and much more challanging than just pressing the fire button.
The conversion tables on the bottom are the larger version of a mod that coverts Knots to KM to distance travelled in Minutes, If you know target speed in Knots for instance you can work out how many Kilometres the target will travel in 10 Minutes by drawing a line between the two values you know to obtain the third unknown.
I use this as well as a EXCEL spreadsheet with all the values up to 44 Knots ploted.