I have one that is a simple calculation. Use the formula, =TRUNC(720/A1). Put that formula in cell A2 on an excel sheet and use cell A1 to enter the lap time in seconds. The result will be the number of laps showing in cell A2.
I also have a chart, and I'm pretty sure
@Rednose58 does as well, that lists the break points for each lap count.
For those of you not spreadsheet savy, using an ordinary calculator:
720 divided by the lap time in seconds and ignore everything to the right of the decimal point.