[mikeash]

Is it really 140 uses, or is it that you breakeven at 140 plastic bags?

This is a significant difference because reusable bags are usually a lot larger and a lot stronger. In my experience, one use of a reusable bag substitutes for something like five plastic bags. That makes the breakeven point arrive a lot faster.

[olejorgenb]

The cotton bags I've seen in Norway are usually about 2/3 the size of a standard plastic bag. I usually just reuse the plastic bags - some bags are needed for garbage so this works well.

[mikeash]

Interesting. In the US, the standard plastic grocery bag is really small, to an almost idiotic degree sometimes. (A particularly large box of cereal may not fit in one at all!) Typical reusable bags are much larger.

[ggm]

This is an excellent question. I've always wanted to know how the 140 is calculated and what assumptions and model it brings to the table.