Many of us take a complicated mixture of different types of Parkinson's drugs, with different doses, at different times. The concept of LED (levodopa equivalent dose) gives a rough way to compare two medication regimes. For instance, 8mg of ropinirole has, very roughly, about the same effect as 160mg of levodopa (taken with carbidopa).
I've been through the literature and found out the conversion factors for many Parkinson's drugs and written a small app to do the calculations: finding the LED for each dose and adding them together to find the LEDD (levodopa equivalent daily dose). This can be run directly from my web site at:
I repeat LED is a rough measure: the conversion factors are estimates, differences between people are not considered, side effects are not included, and the time profile of the drugs is not considered. But, it does give a starting point to discussions of your medication regime.