The Amazon TACoS formula is the following: (ad-spend ÷ total revenue) * 100. To do this on the calculator, follow the steps below. 1- Select a time frame on the ad-console (e.g June 1-29) and copy your ad-spend into the calculator. 2- Select the same time frame on Seller Central (Business Reports) or Vender Central (Retail Analytics > Sales) copy your ordered revenue into the calculator. 3- Done! If you're running any DSP adverts, make sure to add your DSP ad-spend to your search ad-spend before calculating your TACoS.