Coffee does not go off in a way that makes you ill. It goes flat, and it does so on a predictable schedule.
The window
Days 0 to 4 — too fresh. The coffee is releasing carbon dioxide rapidly, which repels water and makes extraction uneven. Espresso from very fresh beans gushes and tastes thin; filter brews bubble aggressively and finish fast.
Days 5 to 35 — the useful window. Enough gas has escaped for water to penetrate evenly, and the aromatics are still there. Espresso often peaks a little later in this range than filter, around days 10 to 21.
Beyond about 6 weeks — the aromatics are going. It still tastes of coffee, and the character that made a particular origin interesting has faded into generic.
Roast date, not best-before
This is the single most useful thing to look for on a bag. A best-before date is a food safety formality and often sits two years out, telling you nothing about when the coffee was roasted. A roast date tells you exactly where in the window you are.
If a bag has only a best-before date, assume it was roasted a long time ago. Roasters proud of their freshness print the roast date.
Once opened
The bag’s one-way valve lets CO₂ out without letting oxygen in — excellent until you open it. After that it is just a bag, and the coffee starts oxidising.
Move it to an opaque airtight container, or roll and clip the bag tightly. Two to three weeks before you notice a decline.
Ground coffee
About fifteen minutes for the volatile aromatics that make coffee interesting. This is not an exaggeration and it is why a grinder matters more than a machine.
Questions people actually ask
Can I still use beans that are three months old?
Yes, and expect flat, generic coffee. Darker roasts hold up marginally better because there was less delicate aromatic character to lose.
Do beans go stale faster in a warm kitchen?
Yes. Heat accelerates oxidation, as does light. An opaque container in a cupboard rather than a glass jar on a sunny worktop makes a measurable difference.
Last reviewed 8 August 2026