eCommerce Fee Calculations and Displaying Mathematical Formulas in WordPress

Paul — Wed, 29 Apr 2009 20:28:55 +0000

It’s funny how solving problems and finding new creative solutions can be a source of pleasure. Recently a client requested credit card payment for services rendered using a popular online eCommerce payment service. Since my volume with that service is low, the fee is high – 2.9% plus $0.30 which is subtracted from the invoiced amount. I also have to spend the time setting up the online invoice within that system. After speaking to the client they agreed to cover the fee. So the question becomes “What calculations do I make to figure out the fee to add on so that I don’t lose money?” After confirmation by two esteemed colleagues over gelato at the Bellagio*, the formula is ready to be shown to the world! I’ve also found a nifty WordPress plugin that displays mathematical formulas based on simple text notation!

x is the amount billed for, y is the tack on amount to cover the fee, x + y would be the amount on the invoice be set up with the payment service.

Example: I want to collect $840. What should the online invoice be?

The invoice billed through the service should be $865.40.

The formula plugin is called “wpmathpub” and makes displaying my text entry of y = (.029x+.3)/(1-.029) into the first mathematical formula displayed above. It does require some additional configuration that is not standard with most hosting accounts, but then you’re with a hosting company that provides first class service, right? (If not, please contact us!)

*Thank you Adi and Leslie.

Pariah Design, LLC. » eCommerce

eCommerce Fee Calculations and Displaying Mathematical Formulas in WordPress