Walk down a cookware aisle and almost every box tells you the same three things: the diameter, the material, and something about the coating. Almost none of them tell you how thick the base is. That omission is not an accident, because base thickness is the number that most reliably predicts how a pan will behave.
What the base actually does
A burner heats a ring, not a circle. Everything outside that ring gets its heat by conduction sideways through the metal of the base. A thin base has very little cross-section to conduct through, so the ring stays hot and the rest of the pan stays cooler. That is why a cheap pan burns a sauce in a circle in the middle while the edges are still pale.
A thicker base (or a thin one with an aluminium core, which conducts around four times better than stainless) gives that sideways flow somewhere to go. The heat evens out before it reaches the food.
The numbers worth knowing
Under about 1.5 mm you are in disposable territory: it will hot-spot and it is likely to warp the first time it goes from a hot hob into a sink. Around 2.5 to 3 mm with an aluminium core is where a stainless pan starts behaving properly on a domestic hob. Cast iron is typically 4 to 5 mm, which is why it behaves so differently. Carbon steel woks run 1.5 to 2 mm on purpose, trading evenness for response speed.
Disc bases versus full cladding
Many pans have a thick disc welded onto the bottom of a thin body. That works for the base itself, but the wall above it stays thin, so anything that climbs the sides (a risotto, a reduction) scorches at the join. A pan clad all the way up the wall costs more and is heavier. For a frying pan the difference barely matters; for a saucepan it does.
Warping
Warping is thickness plus thermal shock. A thin base expands unevenly, and running a hot pan under a cold tap makes that worse. Once a base has bowed it will spin on an induction hob and never sit flat again. Thicker metal is more forgiving of the mistake, but the real fix is letting pans cool before they meet water.
How to check before you buy
If a listing does not state base thickness, ask. A seller who knows their product will have the figure. Weight is a decent proxy in the meantime: for a given diameter and material, heavier means thicker. A 24 cm stainless frying pan that weighs 600 g has a thin base regardless of whose name is on it, and one that weighs 1.1 kg does not.