Can these two used interchangeably?

We generally consider a jacket to be lighter in weight than a coat.

For me, a jacket extends from the shoulders to somewhere between the waist and the lower part of the buttocks. A coat extends from the shoulders to somewhere between mid-buttocks and anywhere between mid-thigh and ankles.

Jackets may be won indoors or, weather permitting, outdoors. Coats are mainly worn outdoors.

In the US, these can used interchangeably, but "coat" would be used if you wanted. to emphasize that the attire is more formal or expensive:

"We require coat/a jacket and tie here."

"It's going to be cold. Be sure to bring a coat/jacket."

"Wow, where did you get the mink coat/jacket?"