Paint Calculator: How Much Paint Do You Need?

Gallons for walls, ceiling, trim and primer, with cost, for one room or the whole house.

Project Details
Enter your measurements and requirements
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Results
Calculated estimates for your project
Paintable wall area316 sq ft
Ceiling120 sq ft
Wall paint2 gal ($70)
Ceiling paint (flat white)1 gal ($28)
Estimated cost$98
Hiring a painter$872 to $2,616 ($2 to $6 per sq ft)

How much to buy

Low, 5% waste
2 gal
Typical, 10% waste
2 gal
High, 15% waste
2 gal

Formula: Paintable area x coats / spread rate, plus waste, rounded up to gallons and quarts.

  • Dark colours and bare drywall can need an extra coat.

Turn these numbers into a build plan.

  • 316 sq ft paintable area
  • 2 coats
  • 2 gal paint
Materials List
Recommended materials and quantities
Wall paint2 gal
Ceiling paint (flat white)1 gal
Painter's tape, 1.5 in2 rolls
Roller kit, brushes and drop cloths1 set
Ceiling 120 sq ft96 sq ft80 sq ft96 sq ft80 sq ftWalls 352 sq ft before doors and windows

How we got this: 316 sq ft of wall x 2 coats / 375 sq ft per gallon + 10% = 1.85 gal, bought as 2 gal.

Save this room to Blueprint for a checkable shopping list, a prep-to-second-coat plan and a place to log the color for touch-ups. New drywall? Size it with the drywall calculator. Thinking of an accent wall in paper instead? Try the wallpaper calculator; trim lengths are in the trim calculator.

Next you will need

Trim & Baseboard CalculatorFlooring Calculator

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Project plan · built from your numbers

Paint a 12 x 10 ft room (2 gal of wall paint)

Roll 2 coats over 316 sq ft of walls after subtracting 1 door and 1 window. Buy 2 gal of wall paint, 1 gal of ceiling paint (flat white).

Materials
$175
Time
1 day
Level
Beginner
8 steps 8 tools 7 materials
  1. 1

    Clear and protect the room

    Move furniture to the center and cover it, lay drop cloths along the walls, and remove outlet covers, switch plates, and wall hangings.

    • Furniture covered
    • Drop cloths down
    • Plates and hardware removed
  2. 2

    Check for lead before sanding

    If the house was built before 1978, test old paint with an EPA-recognized lead test kit before sanding or scraping. If it tests positive, use lead-safe practices (wet sanding, HEPA vacuum, no dry scraping).

    • Note the year the house was built
    • Test any paint you will sand
    • Wear an N95 or better while sanding
  3. 3

    Patch, sand, and caulk

    Fill nail holes and dents with spackle, sand smooth once dry, caulk gaps at trim, and wipe the walls down to remove dust and grease.

    • Spackle holes
    • Sand and wipe
    • Caulk trim gaps
01 · Your numbers
Paintable area
316 sq ft
Coats
2
Paint
2 gal
Est. cost
$175
02 · The plan

8 steps · 8 tools · 7 materials

5 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

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Paint a 12 x 10 ft room (2 gal of wall paint)

Finished in 1 day · $175 DIY

Built for your paintable area of 316 sq ft. Your first plan saves free. No card needed.

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Borrow these 8 tools from neighborsFull how-to guide: Paint a room

How much paint for a typical room

A 12 x 12 room with 8 ft ceilings, one door and one window has 348 sq ft of wall. Two coats take about 2 gal of wall paint, plus 1 gal of flat ceiling white.

Paint needed by room size

Two coats at 375 sq ft per gallon, 8 ft walls, one door and one window unless noted, no extra added
RoomWallsCeilingTrimPrimer (new drywall)
10 x 10 bedroom2 gal1 gal2 qt2 gal
10 x 12 bedroom2 gal1 gal2 qt2 gal
12 x 12 room2 gal1 gal2 qt2 gal
12 x 14 room2 gal + 1 qt1 gal2 qt2 gal + 1 qt
14 x 16 living room2 gal + 2 qt1 gal + 1 qt1 gal3 gal
18 x 18 great room3 gal2 gal1 gal3 gal + 2 qt
5 x 8 bathroom1 gal1 qt1 qt1 gal
10 x 12 kitchen (half the wall is cabinets)1 gal-1 qt1 gal
16 x 20 living room, 12 ft vaulted4 gal + 2 qt2 gal1 gal4 gal + 2 qt

How to calculate how much paint to buy

Gallons = (perimeter x wall height - doors - windows) x coats / coverage per gallon.

  1. Measure the walls. Add the length of every wall (the room's perimeter) and multiply by the wall height.
  2. Subtract doors and windows. About 21 sq ft per door and 15 per window, or measure your own.
  3. Multiply by coats. Two coats for a color change or a new finish; one coat is enough only for the same color over a sound finish.
  4. Divide by coverage. Use the can's coverage, usually 350 to 400 sq ft per gallon; textured walls cover about 15% less.
  5. Add ceiling, trim and primer. Ceilings are length x width in flat ceiling white, trim is about 1 quart per 100 linear feet, and primer is one coat at about 250 sq ft per gallon.

Paint coverage by surface

SurfaceSq ft per gallon, per coat
Smooth, painted drywall350 to 400
Textured or orange peel drywall300 to 350
New drywall (after primer)350 to 400; primer 250 to 300
Flat ceiling350 to 400
Wood paneling or trim350 to 400
Brick, block or stucco150 to 250

Cans come in quarts (about 90 sq ft), gallons (350 to 400 sq ft) and 5 gallon buckets (1,750 to 2,000 sq ft), which usually cost about 10% less per gallon. Prep matters as much as the paint: see the painting cheat sheet, the caulk guide and the sanding grit guide. Patching first? Match the wall with the drywall texture repair guide. Refinishing an existing deck? Use the deck stain calculator and refinishing steps.

How to measure a room for paint

Measure the length of each wall at the floor and the height from floor to ceiling. Add the walls to get the perimeter; a rectangular room is 2 x (length + width). Count doors and windows and measure one of each if they are not standard. Vaulted walls are a rectangle plus a triangle: add half the width x the extra rise. The same room size gives you flooring in the flooring calculator.

Painting estimate: DIY cost vs hiring a painter

Doing it yourself costs the paint plus about $75 in tape, rollers, brushes and drop cloths. Painters charge about $2 to $6 per square foot of wall (more with high ceilings, lots of trim or dark color changes), and $1.50 to $3 per linear foot of trim. A 12 x 12 bedroom with ceiling and trim typically runs $400 to $1,000 hired, against about $150 DIY.

Paint calculator FAQ

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

About 2 gal of wall paint for two coats on 8 ft walls with one door and one window, plus 1 gal of ceiling paint.

How many square feet does a gallon of paint cover?

350 to 400 sq ft per coat on smooth, painted drywall. Textured walls get about 300, new drywall soaks up more (prime it first), and brick or stucco 150 to 250.

Should I buy quarts or a gallon?

A quart covers about 90 sq ft. Two quarts usually cost about as much as a gallon, so once you need three quarts, buy the gallon. The calculator rounds that way.

How much paint do I need for a ceiling?

Length x width / 375 per coat. A 12 x 12 ceiling is 144 sq ft, so about 3 quarts for two coats; a 1 gallon can covers it with some left for touch-ups.

Does paint and primer in one replace primer?

Over sound, previously painted walls of a similar color, usually yes. New drywall, patches, stains, glossy surfaces and big color changes still need a real primer coat.

How much paint for an accent wall?

A 12 x 8 ft wall is 96 sq ft: about 2 quarts for two coats. Deep accent colors may need a third coat or a gray-tinted primer.

How much paint should I keep for touch-ups?

About a quart per room. The calculator adds 10% by default; label the leftover can with the room, color and date.

How much paint for the outside of a house?

Exterior siding is a different job: measure each wall face plus gable triangles and expect 250 to 350 sq ft per gallon on wood or stucco. Use the total area mode for an estimate.

How much does it cost to paint a room?

DIY, about $80 to $200 for paint and supplies for a typical bedroom. A painter charges about $2 to $6 per sq ft of wall, or $400 to $1,000 for a 12 x 12 room with ceiling and trim.

How do I measure a room for paint?

Measure each wall's width at the floor and the ceiling height, then count doors and windows. For odd rooms, switch to wall-by-wall and enter each wall.

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