I'm with Ed on this one - if you mark the dipstick when the pan is level, then the only accurate way to check you
oil is to level it every time you check the
oil. If you make it where the
oil will most often be checked, say in your driveway or garage, it'll be accurate every time you check it in that spot.
It's really easy -
1- Find out from the manufacturer of your pan how many quarts are in the pan itself when the entire system is full. Don't count the oil in the engine filter, cooler and lines, etc.
2- Drain the oil in the pan.
3- Fill the pan to capacity minus one qt. You can VERY safely run the engine down one quart for a moment. Place the car where you'll most often be checking the oil. Give the car 10 minutes with the engine off in that location for all the oil to drain down into the pan. Mark a very noticeable line on the dipstick at that level. That becomes your "one quart low - add oil" line.
4- Add one more quart of oil. Give it 10 minutes for the newly added oil to drain down to the pan. Make a second very noticeable line on the dipstick at the oil level with the one additional quart added. That becomes your "full" line.
5- Go have a cold beer. You're done.