How long do potatoes last before they go bad?

Stored properly — somewhere cool, dark and ventilated, not the fridge — a whole raw potato typically keeps for one to two months, and often longer for a firm-skinned variety bought in good condition. Left on a bright counter or crammed into a cupboard with poor airflow, the same potato can start sprouting or softening within a couple of weeks. The gap between those two outcomes has almost nothing to do with the potato itself and almost everything to do with where it sat.

A potato is still alive, and that changes everything

Most vegetables in a fridge are effectively dying slowly from the moment they are picked. A potato is different: it is a storage organ built by the plant specifically to survive underground for months, dormant but not dead, waiting for spring. That dormancy is the entire reason a potato can outlast a courgette by a factor of ten — but dormancy is a state, not a guarantee, and the wrong conditions wake it back up early. Light, warmth and moisture are the three signals that tell a dormant potato it is time to start growing again, which is exactly the process that shows up in your kitchen as sprouting.

Why the fridge makes it worse, not better

The instinct to refrigerate anything that might spoil runs into a genuine exception here. Below about 7°C, an enzyme inside the potato starts converting its stored starch into sugar faster than the potato would manage at room temperature. The potato itself does not look any different, but it tastes unexpectedly sweet and browns much more aggressively when fried or roasted, because there is now extra sugar available to caramelise. None of that is a safety issue — it is a quality one, and an easily avoidable one, since a cool cupboard does the actual job of slowing spoilage without triggering the sugar conversion a genuinely cold fridge does.

The two signs, and what they actually mean

A potato that has been sitting for a while tends to show one of two visible changes, and they are worth telling apart rather than treating as interchangeable warning signs.

Sprouting. Small pale shoots emerging from the eyes are the potato acting on exactly the signal described above — it has decided conditions are right to grow. A few small sprouts on an otherwise firm potato are extremely common and do not mean the whole potato is finished; most food-safety guidance treats this as something to deal with at the point of preparing it, not a reason to throw the potato out on sight.
Greening. A green tinge on the skin, usually where the potato was exposed to light, signals a rise in a natural compound called solanine, which is also linked to the sprouting process and can taste bitter. This is treated more cautiously than sprouting in official food-safety guidance, and how much of a potato is affected — a small patch versus a potato that is extensively green or soft throughout — makes a real difference to what guidance recommends doing with it. This is a case worth checking against your own country's food-safety advice rather than judging purely by eye, since the guidance is specifically about a compound you cannot see or smell your way to a verdict on.

A potato that has gone soft, wrinkled, visibly mouldy, or that smells distinctly off is a different and simpler case — that is ordinary spoilage, and the usual rule applies: past that point, it is not a potato you rescue by trimming.

What actually speeds things up

Light. Even indirect daylight through a kitchen window is enough to trigger both greening and sprouting over time, which is why a paper bag or a closed drawer does more for a potato than an open bowl on the counter, however nice the bowl looks.
Warmth. A cupboard next to the oven or above a fridge motor runs warmer than the rest of the kitchen without feeling obviously hot, and that small, constant difference is enough to shorten a potato's dormancy noticeably over weeks.
Trapped moisture. A sealed plastic bag holds in the humidity a potato naturally gives off, which encourages both sprouting and the soft, mouldy spots that come from rot rather than simple ageing. A paper bag, a wooden crate, or an open basket lets that moisture escape instead of sitting against the skin.
Ethylene from other produce. Onions, apples and other ethylene-producing fruit stored right next to potatoes hurry the same dormancy-breaking process along, which is also the reason the old advice to keep potatoes and onions apart is not just kitchen folklore.
One bad potato in the bag. A single potato that has started to rot releases moisture and gas that nudge its neighbours in the same direction, so a bag is only as good as its worst member — worth a quick look through occasionally rather than assuming the whole batch is fine because the top one is.

What actually helps

Somewhere cool, dark and ventilated — not the fridge. A cupboard away from the oven, a pantry shelf, or a cellar if you have one, all beat both a bright countertop and a cold fridge.
A paper bag or open container, not sealed plastic. Airflow does more for a potato than an airtight seal ever will.
Keep them away from onions. Store the two separately even though they often get sold, and shopped for, together.
Buy roughly what you will use in the window you actually have. A bag stored well for a month is a better plan than a bag stored badly for a week, and knowing which cupboard has a working cool, dark spot matters more than the brand or variety on the label.

The part that is easy to lose track of is simply which cupboard a bag ended up in and how long it has actually been there, especially once a bag of potatoes migrates from the pantry to a spot near the oven because that is where there was room on a busy day. Munch lets you log an item against where it is actually stored — fridge, freezer or pantry — so a bag of potatoes has an honest age attached to it, visible to everyone in the household, rather than depending on whoever bought it remembering which shelf they used.

None of this needs a rulebook memorised in advance. A potato is built to last for weeks on its own, provided it is kept somewhere that does not ask it to wake up early — cool, dark, dry, and away from the fruit and vegetables that would otherwise nudge it along.