Obviously, no one is going to run out to the grocery store to buy just enough beans – or ground coffee – to make a single cup or pot. That means we have to talk about the shelf life of coffee. 

Let’s start with how long coffee beans last. They’re at their freshest for seven to ten days after they come out of the roasters, which is why reputable coffee producers print a “roasted on” date on their packages. That date helps you purchase the freshest beans possible. (Ignore the “expiration date” you may see on some packages, since it’s relatively meaningless. There’s no such thing as “expired” coffee, just old coffee that’s gone stale.)

Why do beans begin to lose freshness after a week or so? Once again, as Ron Burgundy would say, it’s science.

As coffee beans are roasted, they begin to release carbon dioxide in a process known as degassing. They’re still releasing CO2 after they’re packaged, which is why you’ll see a small vent hole in most of the packages sold by quality coffee roasters. The hole is actually a one-way valve that lets carbon dioxide out, but prevents oxygen and moisture from getting in. In about a week, once the degassing has finished, oxidation will begin. 

The valve delays oxidation, but it can’t completely stop it from occurring. That’s the reason that coffee beans are best used within a week or two of their roasting date, and why it’s always a good idea to only purchase the amount of beans you will be using that month.

(Vacuum-sealed coffee packaging is not as desirable and should be avoided if possible. Carbon dioxide released by the beans is forced to stay in the vacuum-sealed bag, where it can damage the beans’ flavor or even cause the bag to explode.) 

Ground coffee oxidates more quickly than whole beans, because it has a much larger surface area exposed to the air. Naturally, that means ground coffee should be used even more promptly than beans. About two weeks after you’ve opened a package of ground coffee, it will no longer be fresh.

The news isn’t all bad, though. It won’t be quite as good as it was right after roasting, but whole bean coffee can last about six months when stored properly. If you vacuum-seal and freeze it, it can last for a couple of years – although it definitely won’t taste as good when you thaw it out, grind it and brew it.

Ground coffee’s unopened shelf life, as you’d probably expect, is shorter. Figure 3-4 months before you’ll have to throw it away or repurpose it. And it can last at least a year if you put it, vacuum-sealed and unopened, into the freezer. (Again, caveat emptor on the freezer thing.) Pods like Keurig K-Cups can last a few months longer. Prefer decaf coffee? The time frames are about the same.

Those who use instant coffee often keep a jar in their refrigerator until they use it up or until the world ends, whichever comes first. That’s not the best idea. No matter what expiration date they print on the jar or bottle, instant coffee will start to go bad within two weeks of opening the container. If you leave it sealed, you should have a year or two before it goes bad.

The Best Ways to Keep Coffee Fresh

You can’t keep coffee fresh indefinitely, but you can stave off the inevitable oxidation that will render it stale and bitter.

The key consideration is where you keep your coffee. First of all, never keep beans or ground coffee in their store packaging, and don’t put them in a random canister that you keep on the counter. Always store coffee in an opaque, airtight container, in order to keep out as much oxygen and light as possible. That limits oxidation and “photodegradation,” the process by which atmospheric elements change the chemical makeup of the coffee. Containers made of ceramic, glass or stainless steel are best.

Keep the container tucked away from the elements; a closed cabinet or pantry is best, as long as it doesn’t get too hot or cold. Coffee should be stored in a dry place and at room temperature, because heat, drastic changes in temperature, and humidity can cause condensation to form and the oxidation process to speed up. That also means that a cabinet right over the stove should be off-limits, no matter how close it is to your coffee maker.

What’s the best way to regularly enjoy fresh coffee? Aficionados often shell out extra money to have small quantities of beans regularly delivered to their home. It’s a pricey solution – but it ensures that they always have the freshest coffee on hand.