Go wide and shallow, not tall

The right lunch box size is about 1.5 to 2 liters — roughly 9 by 7 inches and no more than 3 inches tall.

Height is the constraint. Most office fridge shelves give you 8–10 inches of vertical clearance, so almost any container fits if it’s low-profile. The thing that gets rejected is a tall soup jar or a deep casserole dish that hits the shelf above or falls over in a full fridge.

Volume-wise, 1.5 liters covers a proper meal — protein, carbs, veg. Go to 2 liters if you eat big portions or bring a side. That’s still only about the size of a standard meal-prep container, and it slides onto a shared shelf without stealing someone else’s space.

Before you buy, measure the actual fridge compartment where you plan to put it. One tape measure trip beats a week of guessing and eating cold salad out of a Tupperware you can’t close.

The fridge is everyone’s territory now. Don’t bring the container that makes it everyone’s problem.