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Blessed Arc Media

Paint Calculator: How Much Paint Do I Need?

Get a real number before you go to the store.

A gallon covers about 350 to 400 sq ft on smooth walls and less on texture. Enter your room and we'll tell you how much primer and paint to buy, with 10% extra built in for waste.

Perfect for DIY homeowners, painting contractors, property managers, and real estate flippers.

This calculator is for you if…

First time painting a roomTired of making multiple store tripsHave textured wallsDoing a color change
PAINT CALCULATOR

How Much Paint Do I Need?

Get an accurate estimate for primer and paint based on your room dimensions and surface texture.

Room Details

Coverage: 375 sq ft/gal paint, 350 sq ft/gal primer

$

Enter your paint price to see estimated total cost

Your Paint Estimate

Primer

1.5

gal

Paint

2.5

gal (2x)

Total

4.0

gal

Est. Cost

—

enter price

Shopping List

Buy 2 gallons of primer

Buy 3 gallons of paint

Estimate only. Test a small area first. Actual coverage varies by paint brand, application method, surface condition, and technique.

Show the Math

Net Coverage Area: 400 + 0 - (1 doors × 20 + 2 windows × 17.5) = 345 sq ft

Primer: (345 ÷ 350) × 1.1 waste factor = 1.5 gal

Paint: (345 ÷ 375) × 2coats × 1.1 waste factor = 2.5 gal

Why add 10% waste? Paint is lost to roller nap, brush absorption, drips, touch-ups, and uneven surfaces. Planning for 10% extra prevents mid-project store runs.

Tool powered by Blessed Arc Media - Web Design for Home Service Businesses

Quick Reference: Coverage by Texture

Smooth Drywall: 350-400 sq ft/gallon

Orange Peel: 300-350 sq ft/gallon

Knockdown: 250-300 sq ft/gallon

Popcorn/Heavy: 200-250 sq ft/gallon

Stucco/Brick: 150-200 sq ft/gallon

What Makes This Paint Calculator Different

Most calculators assume one flat coverage number. That's fine on smooth drywall, but it leaves you short the second your walls have any texture to them.

Texture-aware

It adjusts for your wall texture

Smooth, orange peel, knockdown, popcorn, stucco, brick. Texture drinks more paint, so we change the math to match the wall you actually have instead of pretending every wall is flat.

Primer included

It includes primer, not just paint

Most calculators only count the paint and leave you guessing on primer. We tell you both, so you walk out with the primer the job actually needs and not a can more.

No second trip

It builds in waste and hands you a shopping list

We add a 10% waste factor and round up to whole cans, so you don't run out halfway through and make a second trip. Then you get a clean shopping list you can download as a PDF.

How Many Gallons of Paint Do You Need?

Ballpark numbers for two coats on smooth walls, so you can check yourself before you buy.

Paint by square feet

200 sq ft1.5 gal
400 sq ft2.5 gal
600 sq ft4 gal
800 sq ft5 gal
1,000 sq ft6 gal
1,500 sq ft9 gal

Paint by room

Bedroom (12×12)~400 sq ft walls, 8' ceiling
2 gal paint
Living Room (16×20)~576 sq ft walls, 8' ceiling
3 gal paint
Bathroom (8×10)~288 sq ft walls, 8' ceiling
1-2 gal paint
Kitchen (12×16)~448 sq ft walls, minus cabinets
2 gal paint
Master Bedroom (14×16)~480 sq ft walls, 8' ceiling
2-3 gal paint
Hallway (4×20)~384 sq ft walls, 8' ceiling
2 gal paint

This is paint only, two coats, smooth walls, with 10% waste already added. Texture, primer, and color changes add more, so use the calculator above for your exact numbers.

How the Calculator Works

No black box. Here's exactly how we calculate your paint estimate.

The Calculation

Step 1: Net Area = Wall + Ceiling - (Doors × 20) - (Windows × 17.5)

Step 2: Primer = (Net Area ÷ Primer Coverage Rate) × 1.10 waste

Step 3: Paint Coats = 2 (or 3 for color change)

Step 4: Paint = (Net Area ÷ Paint Coverage Rate) × Coats × 1.10 waste

Why 20 sq ft per door?Standard interior door is 6'8" × 2'8" (about 18 sq ft) plus the frame area you don't paint. Windows average 3×5 ft (15 sq ft) plus trim.

Key Assumptions

  • •10% waste factor: Accounts for roller absorption, brush waste, drips, and touch-ups
  • •Two coats standard: Industry best practice for proper coverage and durability
  • •Three coats for color change: Going dark to light requires extra coverage to block bleed-through
  • •Half-gallon rounding: Results round to nearest 0.5 gal; shopping list rounds up to whole gallons

What This Calculator Doesn't Include

  • • Paint for trim, doors, or cabinets (different calculation)
  • • Extremely porous surfaces (bare concrete, new stucco)
  • • Spray application (uses 20-30% more paint)
  • • Varying paint quality (premium paint covers better)
  • • Dramatic color changes (dark to white may need 4+ coats)

Tip: When in doubt, buy an extra gallon. Unopened paint can be returned, and having touch-up paint is always useful.

Last updated: June 2026

Coverage rates based on Sherwin-Williams, Behr, and Benjamin Moore specifications.

Built by: Blessed Arc Media

Web design for home service businesses.

How Do I Use This Calculator?

Access this tool instantly from your phone, or add it to your website to help your audience.

Save This Tool for Quick Access

Open this tool anytime, just like a calculator on your phone. No app to download.

1

Copy the direct link

https://blessedarcmedia.com/t/paint-calculator
2

Add to your home screen or bookmarks

3

Open it anytime you need it

Tap your home screen icon or bookmark. Works just like opening the calculator on your phone.

Common Paint Questions

How much paint and primer you need, why texture and two coats matter, and how to put this calculator on your own site.

For a standard 12x12 room with 8-foot walls, plan on about 2 gallons of paint for two coats on smooth walls, plus primer if you need it. That covers the four walls minus a normal door and a window or two. Taller ceilings or textured walls push it up from there. Put your real numbers in above and you'll see exactly where you land.

About 350 to 400 sq ft on smooth walls for one coat. Texture pulls that down: orange peel runs about 300 to 350, knockdown about 250 to 300, popcorn about 200 to 250, and stucco or brick about 150 to 200. Those rates are based on Sherwin-Williams, Behr, and Benjamin Moore. Most jobs need two coats, so cut those numbers roughly in half for what the room actually takes.

About 3 gallons for two coats on smooth walls. That's paint only. If you're priming bare drywall or covering a big color change, add for that, and texture adds more too. Run your texture through the calculator above for the real figure.

Usually yes, and most calculators skip it. Prime bare drywall, patched spots, stains, and anytime you're making a big jump like dark to light. Primer covers at about the same rate as paint, so figure roughly one coat over the area that needs it. If you're repainting a clean wall a similar color, you can often skip it, and the calculator leaves that call to you.

A textured wall isn't really flat. All those bumps and pits add surface area, and every bit of it has to get coated, so the same square footage soaks up more paint than smooth drywall would. Use a smooth-wall number on a textured wall and you'll come up short partway through. That's the most common reason people run out mid-job, and it's why we ask for your texture up front.

Two coats is what real coverage takes. One coat almost always looks thin and patchy, especially over a different color or fresh primer, and the color won't be true. A second coat evens it out and gives you the finish you're paying for. Going from a dark color to a light one can even need a third, and the calculator accounts for that.

Yes, and it's free to embed. It keeps a small "Powered by Blessed Arc Media" link at the bottom, and that's it. Painters, builders, hardware stores: it's a genuinely useful thing to hand your visitors. You'll find the embed code in the "Add to My Website" section on this page, and if you get stuck dropping it in, just message me.

Yes, completely free, and there's no signup. Enter your room, get your primer and paint amounts, download the PDF, done. We built it to actually be useful, and we'd rather you remember where it came from than charge you for it.