How much paint do I need for a 12x12 room?

A 12×12 room with 8-foot ceilings has about 384 sq ft of wall area. Subtract a door and a window and you're left with roughly 350 sq ft, which is about 1 gallon per coat on smooth walls. So 2 gallons for the standard two coats. Textured walls need about 15% more.

How many square feet does a gallon of paint cover?

About 350 sq ft per gallon on smooth, previously painted walls; closer to 300 sq ft on textured surfaces, and 250-300 on porous or bare surfaces that drink the first coat.

How much does a gallon of paint cost in Bellingham?

At Bellingham retail, meaning Sherwin-Williams on Iowa Street or Benjamin Moore at Hardware Sales, expect $45-$85 per gallon depending on line and finish, before contractor or sale discounts.

Do I really need two coats?

Almost always yes for a color change or a quality finish. One-coat claims hold only for same-color refreshes on well-prepped walls. Deep colors over light (or the reverse) can need a tinted primer plus two finish coats.

How Much Paint Do I Need? Free Calculator from Bellingham Painting Co.

Methodology

The coverage math, shown

Wall area = wall length × ceiling height, minus 21 sq ft per standard door and 15 sq ft per window. Coverage: 350 sq ft per gallon on smooth previously painted walls, 300 on textured, 275 on bare or porous surfaces that drink the first coat. Multiply by coats, then round up to whole gallons per coat. We always round up because running out mid-wall shows as a lap mark forever.

Cost basis: $45-$85 per gallon is what Bellingham retail actually charges as of July 2026 for quality-line interior acrylics at Sherwin-Williams (Iowa St) and Benjamin Moore at Hardware Sales, before promotions. Supplies (tape, plastic, roller covers, cut brush) typically add $40-$90 per project. Last reviewed July 2026.

The mistakes this calculator prevents

Forgetting the second coat. Nearly every color change needs two finish coats. "One-coat" marketing holds only for same-color refreshes.
Trusting the can's max coverage. 400 sq ft/gal assumes ideal smooth surfaces and a thin spread rate. Real rooms with texture and touch-in average less.
Buying gallons across two trips. Tint batches vary. Buy everything at once and have the store box (intermix) the gallons.

And if the math says nine gallons across three rooms of cutting-in and ceiling work, that's usually the point where people call us. Interior painting runs $4.40-$8.25 per floor sq ft in Bellingham; try the cost calculator to compare against your weekend.

Common questions

Paint quantities, answered

How much paint do I need for a 12×12 room?

About 350 sq ft of paintable wall after a door and window. That's 1 gallon per coat on smooth walls, so 2 gallons for the standard two coats. Textured walls: add roughly 15%.

How many square feet does a gallon really cover?

Plan on 350 sq ft on smooth, previously painted walls, 300 on texture, and 250-300 on bare or porous surfaces. The 400 sq ft on the label is a best-case number.

What does paint cost per gallon in Bellingham?

$45-$85 at local retail for quality lines, depending on brand tier and finish. Contractor accounts and sales bring that down, which is one reason a pro bid isn't just "your gallons plus labor."

Should I use the same paint for ceiling and walls?

Use dedicated ceiling paint. The flatter sheen hides roller lap and imperfections overhead. Wall paint on ceilings flashes badly under window light, and Bellingham's low-angle winter sun makes that worse.

How much paint do you actually need?

Your room(s)

The coverage math, shown

The mistakes this calculator prevents

Paint quantities, answered

Or skip the ladder entirely

Got it. We'll call you shortly.