A few days back someone asked a question mowing time with various sized decks. I got to thinking it would be nice to have an Excel sheet, where you could fill in the blanks about mower size, speed, lot size, plus some other variables. With some help from my son, I think we came up with something that some people will find useful.
You just click on the link that Simple_John posted. It will give you a chance to either download the calculator, or just open it up. Fill in the blanks as shown, and it should give you the time, in minutes, that it will take you to complete your mowing.
Couple of notes.
1. Speed. You have to know how many feet per second you will be mowing. This calculator was based on a push mower, but it's easy enough to figure for a rider.
2. Effectiveness. Doubt that anyone is 100% effective. That is for your overlap area, and can also take into consideration of lawn obstacles such as trees, fences, childrens toys, etc.
If you scroll thru this thread you will find an updated mowing calculator, as well as a smartphone calculator. Give them all a try!
Hope this helps out! Let me know if you have any questions.