This story is part of a series on ocean plastics.

Plastic grocery bags were first introduced in America in the late 1970s. Today, they’re ubiquitous and almost always free for customers. The problem is, we don’t know what to do with them when we get them home.

They’re supposed to get recycled, but most aren’t. You probably have a bunch lining your garbage cans, or balled up in a heap under the sink. You’ll see them stuck in trees and wafting lazily in the wind. You might even use them to pick up your dog’s poo.

Many of them end up in landfills, where they can sit for hundreds of years, potentially leaking pollutants into the soil and water. They also clog storm drains and jam recycling equipment. Countless tons of them are floating around in the oceans, and pieces of them can be found in the stomachs of dying or dead sea turtles and whales.

So, just how many plastic bags does the average family use each year? Enter your best guess below.