Mixology is a tool that makes it easy to calculate the ingredients needed for media, buffers, etc. First you enter the final volume of buffer at the top. Then on the left hand side you enter the concentrations desired, in any units (mg/ul, uM, % v/v, etc.). The amounts you need to measure out will appear on the right hand side, in the units that you enter there. Mixology automatically extracts molecular weights from ChEBI to make these calculations as smooth as possible.
If you click "get permalink" you will be redirected to a page with a record of your recipe. Bookmark it and you should be able to get back to it.