How long does opened cheese last in the fridge?

The short version: it depends almost entirely on how much water is left in the cheese, not on price, brand, or how carefully it was made. A block of well-aged parmesan can sit opened in the fridge for a month or more and barely notice. A tub of ricotta opened the same day is pushing it by the end of the week. That is not one cheese being higher quality than the other. Chemically, they are close to different foods — one has had most of its water removed and behaves like a preserved product, and the other is close enough to fresh dairy that it runs on roughly the same clock as an opened carton of milk.

Why moisture is the entire story

Cheesemaking is, at its core, a controlled way of removing water from milk. Curds are cut, drained, sometimes pressed, sometimes salted and aged for months — and every one of those steps pulls more moisture out. How far that process goes is what actually determines shelf life, far more than what the cheese is called or where it sits in the shop. A hard, aged cheese can have as little as a third of the water content of a soft fresh one, and bacteria and mould both need available water to establish themselves, the same limiting factor that makes salt and sugar work as preservatives elsewhere in the kitchen. Age and salt content push the same direction again: a well-aged hard cheese is, structurally, closer to a cured product than to fresh dairy, while a fresh soft cheese is barely a step removed from the milk it was made from a day or two earlier.

Three rough groups, three different windows

• Hard and aged — parmesan, aged cheddar, pecorino, aged gouda, manchego. These keep the longest by a wide margin: weeks once cut, sometimes over a month, if wrapped reasonably well. Low moisture and a firm structure mean bacteria and mould struggle to spread through the cheese even if a small patch appears on the surface.
• Semi-soft — mozzarella blocks, deli-sliced cheese, string cheese, a whole brie or camembert. A middle ground: usually good for one to two weeks once opened or cut, longer than a fresh cheese but nowhere near a hard one. These carry noticeably more moisture than the aged group, without being anywhere near as wet as a fresh curd cheese.
• Fresh and soft — ricotta, cottage cheese, cream cheese, fresh mozzarella sitting in liquid, mascarpone, burrata. These behave like dairy in a semi-solid shape, because that is essentially what they still are. Once opened, treat the tub the way you would an opened carton of cream or milk — roughly a week, sometimes less — rather than the way you would treat the block of cheddar sitting next to it in the drawer.

The pattern is the same one that shows up elsewhere on this site with condiments: the drier and saltier a food is, the more it behaves like its own preservation system, and the wetter and fresher it is, the more it behaves like the fresh food it actually is.

Why mould on cheese is not automatically a discard-everything moment

General food-safety guidance draws a real distinction here, and it follows the same moisture logic. On a dense, low-moisture hard cheese, surface mould tends to stay on the surface, because the cheese itself does not offer the mould an easy path inward — which is why widely used guidance allows cutting away a generous margin around and beneath a spot of mould on a hard cheese and treating the rest as fine. On a soft, high-moisture cheese, the same mould can spread through the whole thing well before it is visible, because there is nothing stopping it from moving through the water content, so the usual guidance there is to treat the whole piece as finished rather than trying to rescue part of it. Mould-ripened cheeses like blue cheese or a bloomy-rind brie are a separate case again — the mould you see there is the intended process, not spoilage — so this trim-or-discard question does not apply to them the same way. As with any food, when something looks or smells clearly off in a way that goes beyond ordinary mould, the safer move is simply to treat it as done rather than second-guess it.

Wrapping changes the outcome more than people expect

Cling film pressed directly onto a cut hard cheese traps moisture against the surface, which is exactly the condition mould needs and the opposite of what the cheese's own low-moisture structure is built for — wax paper or dedicated cheese paper, loosely closed, lets it breathe a little while still keeping it from drying out completely, and is the closer match to how it was likely sold in the first place. A soft fresh cheese has the opposite problem: it needs to be sealed tightly, in its original tub with the lid pressed down or in an airtight container, both to stop it drying out at the edges and to stop it picking up smells from everything else on the shelf, since a fresh cheese's mild flavour has very little to hide behind. Freezing works reasonably well for some hard cheeses destined for cooking — the texture turns slightly crumblier, which barely matters once it is melted into something — but it is a poor match for fresh soft cheeses, which tend to separate and turn watery once thawed.

Why the good cheese still goes to waste

Cheese has a quirk most vegetables do not: a wedge that is a week old looks almost identical to one that is a month old, at a glance, from outside its wrapping. A wilting bag of spinach gives you a visual cue to check on it. A block of cheddar gives you nothing — it just sits there looking the same, whether it was opened yesterday or six weeks ago, which removes the one prompt that usually gets people to notice an item and deal with it. The wedge bought for one specific dinner, cut into once, rewrapped and pushed to the back, is a near-perfect setup for exactly the kind of forgetting this site has covered before, just with an extra twist: even a direct glance at it will not tell you the one fact that actually matters, which is when it was opened.

This is close to what Munch's opened-item tracking is actually for. Marking a cheese as opened starts its own countdown from that day, visible to everyone in the household rather than only to whoever cut into it first, so the wedge at the back of the drawer is not relying on a glance to tell you what a glance genuinely cannot.

None of this needs a memorised list of every cheese in the shop. It needs one question — roughly how much water is in this — and the rest follows: dry and aged keeps for weeks, fresh and wet keeps for about as long as the milk it came from.