Learn Chinese Grammar: 但是(dànshì=but) vs. 可是(kěshì=but) :

Learn Chinese Grammar: 但是(dànshì=but) vs. 可是(kěshì=but) :

但是is more formal, it can be used in colloquial but more often used in news or written language. 但是 has a strongest intensity of tone (tends to give more emphasis to the second clause). 可是 is usually used in spoken Chinese and has a less strong intensity of tone than 但是. 可是 is often associated with negative result (here it also depends on personal preference).

Examples:

The house is new, but it's very dirty.

a.房子(fángzi=house)很(hěn=very)新(xīn=new)，但是(dànshì=but)很(hěn=very)脏(zāng=dirty) 。

b.房子(fángzi=house)很(hěn=very)新(xīn=new)，可是(kěshì=but)很(hěn=very)脏(zāng=dirty) 。(More used for negative result)