Add all the lap times together, then divide the sum by the number of laps.

Example: five laps, 10.1, 10.0 10.1, 9.8, 14.4(crash)
total = 54.4 divide by five you get an average of 10.88. Notice how the one crash KILLS the average... if that fifth lap was even the same as the slower of the other four, the average would be 10.02.

If you average 10.88 for an eight minute run, you finish with a slow 44 lap run, just crossing your 43rd lap right before the tone.

Average 10.02 for eight minutes you finish with 47 laps, skirting the edge of a 48.

This is why clean driving beats hopups. Spending money on practice always gets the most return. I don't know if I said it in this thread or another one, but I recently mentioned that if the balanced pod was good for a tenth a lap, all I'd need to be TQ at my track would be four and a half balanced pods on the car. Or one good clean qualifying heat, as opposed to one my typical five crash horror shows...