Is a kilo bag cheaper, and will it go stale first?

A kilo bag looks like the obvious saving. Then you remember the last one, still half full a month later.

"Buying a 1kg bag was a mistake as it took me too long to get through it," one person wrote on Reddit. So is a kilo actually worth it?

How much a kilo saves

We compared the same coffee in 250g and 1kg bags from the same roaster: 62 coffees from 36 roasters. The kilo was a median 23% cheaper per kilo. For half of them, the saving was between 17% and 28%.

In dollars, a typical 250g bag costs $21, which is $84 a kilo. The typical kilo bag costs $65.50.

The catch: you have to finish it

That saving disappears if you throw out more than about a fifth of the bag. Beyond that point, four 250g bags would have cost you less.

A kilo makes about 55 double shots at 18g each. At two a day, that's under a month.

How to make a kilo last

Split it up the day it arrives, while it's at its freshest. Weigh it into portions you'll get through in a week or so, seal each one, and freeze all but the first.

"I buy a kilo and break it down into ziplock bags and store in the deep freeze."

That's how one buyer does it, and roasters agree. How long the beans keep depends on the seal. Roaster George Howell told Perfect Daily Grind that single portions last a week or two, and anything you want to keep for a month or longer needs vacuum sealing. Vacuum-sealed, frozen beans keep far longer: Barista Hustle found coffee frozen for more than a year still tasted very good.

Write two dates on every bag: the roast date, and the date you'll use it by. Take out one portion at a time.

A kilo makes sense if

• You make two or more coffees a day at home.
• You've tried the coffee before. A kilo you don't enjoy is the expensive way to find out.
• The kilo gets you over the free-postage threshold. Here's how much that usually is.

Each roaster in our picks below has kilo bags that cost more than its free-postage threshold, so one kilo ships free.