When you’re shopping in a local store, it’s easy to find the unit price of virtually any item. Most stores print it right on the price tag, e.g. “$0.02 per square foot”. But when you’re shopping online, unit costs are much harder to locate. Sure, dedicated grocers like Peapod have this info, but other sites — including Amazon — don’t seem to provide it.

Given all the metadata that retailers like Amazon collect for a typical product, calculating and displaying the unit cost seems like a trivial task. By doing so, online retailers could probably entice more people to compare online grocery costs with their local store. They could even run a promotion challenging customers to print out a pre-formatted page with the unit costs of popular products, and then bring it with them to the grocery store. Sure, some things will be a better value locally, but it can’t hurt to pick up more sales on the items that are vastly cheaper online.