How to use the paint calculator
Measure the length and width of the room along the floor, and the wall height from floor to ceiling. Enter how many doors and windows there are — the calculator subtracts about 21 sq ft per door and 15 sq ft per window. Pick the number of coats and whether you are painting the ceiling too.
The result shows the exact gallons plus what to actually buy, rounded up to whole gallons and quarts, and a price range for doing it yourself or hiring a painter in your state.
How paint coverage is calculated
Gallons = (Wall area + Ceiling area) × Coats ÷ 350
One gallon of interior latex covers about 350–400 sq ft per coat on smooth, primed walls. We use 350 to allow for texture, rollers soaking up paint and touch-ups. Rough surfaces like stucco, brick or popcorn ceilings can drop coverage to 200–300 sq ft per gallon.
Example: a 12 × 12 ft room with 8 ft walls has 384 sq ft of wall. Minus one door and two windows that is 333 sq ft. Two coats need 666 ÷ 350 = 1.9 gallons, so buy 2 gallons.
Paint needed by room size
| Room (8 ft walls) | Walls, 2 coats | Ceiling, 2 coats |
|---|---|---|
| Small bathroom (5×8 ft) | ~1 gallon | 1 quart |
| Bedroom (10×12 ft) | ~2 gallons | ~3 quarts |
| Primary bedroom (14×16 ft) | ~2.5 gallons | ~1.25 gallons |
| Living room (16×20 ft) | ~3 gallons | ~2 gallons |
| Whole 1,500 sq ft home interior | ~12–15 gallons | ~8–9 gallons |
How much does it cost to paint a room?
Doing it yourself costs mostly paint: $25–$80 a gallon depending on quality, plus $35–$75 for rollers, brushes, tape, drop cloths and patching. A professional painter charges roughly $1.60–$3.40 per square foot of paintable surface, which usually means $400–$1,100 for an average bedroom. Labor makes up most of that.
| Paint grade | Price per gallon | Good for |
|---|---|---|
| Economy | $25–$35 | Rentals, closets, quick refreshes |
| Mid-grade | $35–$50 | Most bedrooms and living areas |
| Premium | $55–$80 | Kitchens, baths, high-traffic walls, one-coat coverage |
Tips for buying the right amount
- Buy one mixed batch. Tinted paint can vary slightly between batches, so for bigger jobs pour all the cans into a 5-gallon bucket ("boxing").
- Keep a quart for touch-ups and write the room and color code on the lid.
- Trim is extra. Doors, baseboards and window casing usually need about one quart of semi-gloss per room.
- Going light over dark? Use a tinted primer first. It is cheaper than a third coat of premium paint.
Paint cost by state
Painting a 12×12 ft bedroom (walls, 2 coats), hired painter — estimated cost by state. Figures use the same assumptions as the calculator above.
| State | Low | High | vs. US avg |
|---|---|---|---|
| US average | $533 | $1,132 | — |
| Alabama | $464 | $985 | -13% |
| Alaska | $666 | $1,415 | +25% |
| Arizona | $511 | $1,087 | -4% |
| Arkansas | $458 | $974 | -14% |
| California | $650 | $1,381 | +22% |
| Colorado | $549 | $1,166 | +3% |
| Connecticut | $607 | $1,291 | +14% |
| Delaware | $554 | $1,177 | +4% |
| District of Columbia | $613 | $1,302 | +15% |
| Florida | $506 | $1,076 | -5% |
| Georgia | $485 | $1,030 | -9% |
| Hawaii | $703 | $1,495 | +32% |
| Idaho | $501 | $1,064 | -6% |
| Illinois | $586 | $1,245 | +10% |
| Indiana | $506 | $1,076 | -5% |
| Iowa | $506 | $1,076 | -5% |
| Kansas | $496 | $1,053 | -7% |
| Kentucky | $490 | $1,042 | -8% |
| Louisiana | $480 | $1,019 | -10% |
| Maine | $533 | $1,132 | 0% |
| Maryland | $543 | $1,155 | +2% |
| Massachusetts | $639 | $1,359 | +20% |
| Michigan | $533 | $1,132 | 0% |
| Minnesota | $570 | $1,211 | +7% |
| Mississippi | $448 | $951 | -16% |
| Missouri | $522 | $1,110 | -2% |
| Montana | $511 | $1,087 | -4% |
| Nebraska | $496 | $1,053 | -7% |
| Nevada | $554 | $1,177 | +4% |
| New Hampshire | $554 | $1,177 | +4% |
| New Jersey | $623 | $1,325 | +17% |
| New Mexico | $485 | $1,030 | -9% |
| New York | $639 | $1,359 | +20% |
| North Carolina | $474 | $1,008 | -11% |
| North Dakota | $511 | $1,087 | -4% |
| Ohio | $517 | $1,098 | -3% |
| Oklahoma | $469 | $996 | -12% |
| Oregon | $565 | $1,200 | +6% |
| Pennsylvania | $549 | $1,166 | +3% |
| Rhode Island | $586 | $1,245 | +10% |
| South Carolina | $469 | $996 | -12% |
| South Dakota | $480 | $1,019 | -10% |
| Tennessee | $480 | $1,019 | -10% |
| Texas | $490 | $1,042 | -8% |
| Utah | $511 | $1,087 | -4% |
| Vermont | $543 | $1,155 | +2% |
| Virginia | $511 | $1,087 | -4% |
| Washington | $586 | $1,245 | +10% |
| West Virginia | $485 | $1,030 | -9% |
| Wisconsin | $538 | $1,144 | +1% |
| Wyoming | $496 | $1,053 | -7% |
Frequently asked questions
How many gallons of paint do I need for a 12×12 room?
A 12×12 ft room with 8 ft ceilings has about 333 sq ft of paintable wall after one door and two windows. Two coats need about 1.9 gallons, so buy 2 gallons. The ceiling adds about 0.8 gallons for two coats.
How many square feet does a gallon of paint cover?
A gallon of interior paint covers about 350–400 sq ft per coat on smooth, primed drywall. Textured or unprimed surfaces can drop that to 200–300 sq ft.
Do I really need two coats of paint?
Usually, yes. Two coats give an even color and sheen and last longer. One coat can work when repainting the same color with a high-quality paint.
How much does it cost to paint a room in 2026?
Doing it yourself typically costs $100–$250 per room in paint and supplies. Hiring a painter averages about $400–$1,100 for a standard bedroom, and more in high-cost states.
How much paint do I need for a ceiling?
Multiply length × width to get the ceiling area and divide by 350 for each coat. A 12×12 ceiling (144 sq ft) needs about 0.4 gallons per coat.