Wheel size and speedo

I just got some new 16" wheels and i went with 205/45/16 size tires, im wondering how much this is gonna throw off my speedo?

I hope you mean 205/45r16. You should be fine. Theoretically, the overall diameter of these tires is 23.26 inches.

The theoretical overall diameter of stock 195/60r14 is 23.21 inches.

overall diameter in inches = [(width in mm) x 2(aspect ratio) + 25.4(wheel height in inches)] / 25.4