Here's a link to a quick cheat sheet. It's not set up for what you need right now, but I'll tell you what to do.
I made this for lawn care applications in another thread, but it'll be easy to change for your application.
Figure out what you need to charge per 1000 square feet of lawn with variables. I am going to give you some examples, you do it how you want.
Open, flat, no trim 9.00
open, flat, some trim 12.00
few trees, average 14.00
many trees, lots trim, 18.00
Now, what you'll do is put in the type of lawn in the column with the product name. Keep it short, just so you know what it means. Then, in the column that says Oz. per 1000 sq. ft, you put your price per 1000 sq. feet. No $ but you can put in 9.50 or what ever you like. OK, now, you are ready for the calculations. In the yellow box type in the size of the lawn you want to display. (If it is 3500 square feet, you will enter 3.5) You can enter and print out a dozen different sheets for different sized properties and put them in a notebook to carry with you.
Want to simplify? Change things around. In the column that says product, put anything you want, or nothing. In the column that says "Oz. per 1000" put various lot sizes, i.e., (1 for a thousand, 2 for 2000, etc.) Then, after you get your sizes in, just enter your price per 1000 square feet of mow. This will then give you all the prices for the various sized lots. Only thing is that it will not give a different price for different services. Print 1 sheet and you are done.
Any questions, let me know.
Here is the link to the post with the spreadsheet.