The best meal prep lunch box is just a big empty bag.

The best lunch box for holding five or six small containers is a large insulated tote, not a compartmented bento box. Stop looking for something with perfect little slots and just measure what you already have.

The problem with those organized bento boxes is that they force you to use their compartments, but your meal prep containers have their own sizes. One week you’re packing four square deli containers and a soup jar, the next it’s three round ones and a bag of nuts. A big open bag lets you pack however it fits. You want something insulated, with a wide mouth, and a sturdy flat bottom. A soft-sided cooler from a generic brand works fine — the kind you’d take to a picnic.

One thing that matters more than the bag: the containers themselves. If you’re using the standard 2-cup glass meal prep containers, look for a tote that’s at least 10-12 inches wide and deep enough to stand them upright. If they’re lying flat, you need even more space. A cheap IKEA or Coleman cooler bag will do the job. The “meal prep lunch bag” marketing is mostly just nicer fabric and higher price.

Your containers should dictate the bag, not the other way around. Spend your money on good glass containers that don’t leak, and the lunch bag becomes an afterthought.