Best to ask the person making the coat how much cloth you need to be sure and not end up short and have to buy more cloth or waste money buying too much cloth.
A few bits of basic information are helpful like what is the the length of the coat?
If it is cashmere or has a nap, all the pattern pieces have to be cut in the same direction. this could require more cloth. Raglan sleeves, kick vent , pleated back, belt, patch pockets all require extra cloth.