The spreadsheet below allows you to calculate your Critical Power (CP). To do this you will need to complete 2 time trials as hard as you can. The first time trial needs to be between 2 minutes and 5 minutes long. The second time trial needs to be between 12 and 20 minutes long. Make sure you have a break of at least 40 minutes between the two time trials. You can also use time trials from different days but make sure they come from the same 7 day period.
To calculate your CP fill in below the length in seconds of each time trial and next to it your average power for that effort (not your normalized power) then hit enter. Once you have done this the spreadsheet will calculate your CP and W'.