Hello and thanks for your question. Oil paint is very rich and concentrated, so you don't need very much at one time if you're doing a regular oil painting. As you mix it with whatever medium you're using, it will become slightly thinner and flow easier across the surface. If you want to do an impasto technique (thick, chunky brush strokes), you will need more paint. To avoid using too much paint at one time, I would use the smallest amount you think you will need for the section of the painting you're working on, and then add more as you need it.