The ultimate gear ratio chart

With/without Jack shaft. With the red cells marked “engine” and “primary” containing the # 1, the ratio numbers below represent the calculation using the numbers in the vertical column marked engine, and the horizontal columns marked axle. You only need to change the numbers in the red cells and all the other cells will recalculate. If the smallest driver you will ever use should be a 9 tooth, enter that in the red cell above engine year. Same with the horizontal columns marked axle.
This will print on a 5 x 7 piece of paper. I use photo paper, it comes in that size, and because it’s thicker and it’s shiny.