Well, like toysrme said, it depends on a lot of things. It's not a very reliable variable for precise calculations. Throttle position, how clean the engine is, air filter, valve lash, cam, muffler, and on and on. Change one little thing and there goes your VE number and your calculations. Heck, it won't even keep the same VE across the rpm range. You can figure max VE at max torque rpm, but that's your only constant.
What are you trying to calculate?