Calculate the MPC if the MPC figure is not provided. Calculate the MPC by dividing the change in household consumption by the change in household income. Record the figure obtained in decimal form.
Plug the MPC into the output multiplier formula. The multiplier formula is 1 divided by (1-MPC). For example, if the MPC is .8 subtract .8 from 1. Next, divide .2 by 1 to obtain the multiplier. Repeat the process for all of the different MPC figures.
Multiply the spending increase by the multiplier. For instance, an increase of spending of $200 with a multiplier of 5 will lead to a total increase in spending effect of $1,000.