I have said it many times over the years but I will say it again for new entrants like Stephen, who are not set in their ways: there is no need to convert any counts or revolutions to meters or inches during certification and therefore no need to use spreadsheets or measuring tapes. The official method of processing results gets the right answers, but it is an inelegant way of doing things. Just getting the right answers was not good enough for my maths teacher of 55 years ago. He only gave full marks if you used the most elegant methods or proofs.
Take the following example of calculations in certification of a 5-km course with 1-km splits. (Mile splits are only slightly more complicated.) I assume that tire pressure or temperature increases only slightly from beginning to the end of measurement:
400-m calibration crse: 191.57, .55, .58, and .58. Ave: 191.57
Calib factor = 191.57x1.001/0.4 = 479.40 rev/km = 2397.02 rev/5km
The first ride was for 2397.02 rev to locate a temporary finish line. In the second ride, splits were located at intervals of 479.40 rev with zeroing before each split. The temporary finish line gave a reading of 479.20, so the second ride determined the final finish line.
Although calculations are very simple even when factoring in tire pressure and using mile splits, I have programmed my hand-held calculators to do them after entering the calibration rim readings in hundredths of a rev (ie: 57, 55, 58, and 58)