About a week. Opened milk stays good for roughly 5 to 7 days in the fridge, depending on how fresh it was when you opened it.
Milk doesn't have a single hard expiration moment — it has a curve. Fresh milk pushed back into a cold fridge quickly can outlast the same milk that got left on the counter during breakfast.
The printed date is a starting point, but temperature consistency and how carefully the carton is handled after opening decide how much of that week you actually get.
Once opened, milk typically holds for 5 to 7 days in a fridge kept at 40°F (4°C) or colder, assuming it was opened reasonably close to the sell-by date. Milk opened right at the end of that date may only be good for a few more days. Different types vary slightly too — whole milk tends to outlast skim by a day or so, and ultra-pasteurized milk can last a bit longer than regular pasteurized milk once opened.
Sour smell is the giveaway — it's sharp and unmistakable, often described as tangy or almost cheese-like. Also watch for lumpy or curdled texture, a yellowish tinge, or a taste that's off even if the smell seemed borderline. Any one of those is a reason to pour it out rather than risk it.
Return the carton to the fridge immediately after pouring, keep it sealed tightly, and store it on a middle or back shelf rather than the door. If milk is close to its limit but still smells fine, using it in cooked dishes — baking or sauces — is safer than drinking it plain, since heat and the recipe mask minor quality decline without making already-spoiled milk safe. Once it actually smells sour, cooking will not undo that.
Plant-based milks like oat, almond, or soy generally last a similar 5 to 10 days once opened, sometimes a bit longer since they don't contain the same proteins dairy bacteria feed on. Raw, unpasteurized milk is far more perishable and should be used within a few days, since it lacks the heat treatment that slows bacteria in regular store-bought milk. Lactose-free milk follows the same rough timeline as regular dairy milk, since the only real difference is an added enzyme.
Opened milk is roughly a one-week food, but that week shrinks fast with warm handling. Trust your nose over the calendar once you're near the end of it.
Often yes, if it's been refrigerated the whole time and smells and tastes normal. The sell-by date is about retail stocking, not a hard safety line.
Fridges that run above 40°F (4°C), or doors that get opened often, let bacteria grow faster. A fridge thermometer helps you check the real temperature.
Yes, milk freezes for up to 3 months, though texture can separate slightly after thawing. Shake or stir well and use it in cooking if the texture seems off.
Not always — smell is more reliable. Curdling and lumps are late-stage signs; by then the smell is almost always already sour.