I didn't want to hijack StacyK's thread, but someone posted this in response to me on another forum and I thought this may be helpful for some. If you wanted to get really technical then you could probably do all of the math involved related to mcgs etc..but I was told as a general rule that:
1. 5 inches from a roll on roughly equals 1 drop from a dropper
2. 1 spray roughly equals 3-6 drops depending on concentration of the dropper
3. 1 spray equals approximately 15-30 inches from a roll on