The question of what to charge for a room has a boring correct answer: work out what the room costs you, then add the margin you need to run a business. The reason it feels harder than that is that most painters are asked the question on a doorstep, without the figures, and answer from memory of the last room. That habit is how a business ends up charging its cheapest job's price for every job it does.
Start from cost, because it is the only part you control
Wall and ceiling area, coats, your production rate, prep hours and your fully loaded labour cost give the labour figure; area, coats, coverage and paint price give the materials. On the room worksheet's example, 448 square feet at two coats, 180 square feet an hour a coat and two prep hours is 6.98 hours, which at a fully loaded $38 an hour is $265.16 of labour. That number is not a price, it is the floor beneath one.
Add margin as margin, not as a markup
The price that leaves the margin you want is cost divided by one minus the margin. At 35%, a job costing $1,526.86 prices at $2,349.01; multiplying that cost by 1.35 instead would give roughly $290 less and a margin nearer 26%. Every painting business that quietly earns less than it thinks is making some version of this mistake, on every job, all year.
Then look at the market, and decide separately
Cost plus margin tells you the price you can accept, not the price the job will fetch. Whether you go above it because you are booked out, or hold it because you want the customer's exterior next spring, is a business decision made with the floor in front of you. What you must not do is discover afterwards that you priced below the floor because you never worked it out.
Answering the customer who asks why
A price built this way can be explained in one sentence: this much surface, this many coats, this much preparation, at our rate. That is a far stronger position than a number from memory, and it also lets you offer real alternatives, one coat over a similar colour, or the walls without the ceiling, that change the work rather than simply discounting it.
Questions people ask about how much to charge to paint a room
Should I quote by the room or by the hour?
By the room, priced from hours. Customers understand a job price and dislike an open meter, and quoting a job price keeps the conversation about scope rather than about your hourly rate.
Is there an average price for painting a room?
Averages exist and none of them describe your next room. Ceiling height, trim, condition, colour change and access move the hours far more than the room's floor area does, which is why this site publishes no rate.
What margin should I aim for?
Whatever covers your overheads and leaves a return, which you can only know from your own figures. The important discipline is applying it as a margin consistently rather than adding a different-feeling number to each quote.
How do I handle a customer who has a cheaper quote?
Compare scope, not price. Coats, preparation and what is included differ between bids far more often than rates do, and setting the two scopes side by side is a more honest conversation than discounting.