Back-to-school sales starting in July is the summer version of Black Friday sales starting in October. You can let it make you antsy, or you can use it as a de-stressing strategy. Starting early means you can avoid that wave of chaotic preparations that hits the week before school starts.

Amazon's Back-to-School sale has everything from classroom essentials and lunchtime favorites to the latest tech, with deals up to 50% off.

FinanceBuzz researched what it costs to buy common school supplies at some of the country's largest retailers. Here's which store is the most affordable.