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Paint Calculator

Estimate paint gallons for walls, ceilings, and trim

Room Dimensions
ft
ft
ft
qty
qty
Paint Specifications
#
sq/gal
$/gal
Options
%
Recommended Purchase
--
Total Cost
$0
Wall Area 352 sq ft
− Deductions −35 sq ft
+ Waste Buffer +32 sq ft
Net Paintable 349 sq ft
Net Area 0 sq ft
Precise 0.00 gal

Paint Grade Comparison

See how much budget, standard, and premium paint will cost for your current room dimensions. Switch back to the Calculator tab and change your room size — these numbers update automatically.

Budget
Coverage: 300 sq ft/gal
Price per Gallon
$25
Gallons Needed
—
Total Cost (2 coats)
—
Best for: Rentals, practice rooms, short-term projects
Most Popular
Standard
Coverage: 350 sq ft/gal
Price per Gallon
$45
Gallons Needed
—
Total Cost (2 coats)
—
Best for: Living rooms, bedrooms, everyday use
Premium
Coverage: 400 sq ft/gal
Price per Gallon
$70
Gallons Needed
—
Total Cost (2 coats)
—
Best for: High-traffic areas, kitchens, kids' rooms

Paint Finish Guide

Choosing the right finish is as important as choosing the right color. Each sheen level has trade-offs between durability, cleanability, and how it handles imperfections.

FinishSheenWashabilityHides ImperfectionsBest For
Flat / MatteNoneLowExcellentCeilings, low-traffic rooms
EggshellLowModerateGoodLiving rooms, dining rooms
SatinMediumGoodFairBedrooms, hallways
Semi-GlossHighExcellentPoorKitchens, bathrooms, trim
High-GlossVery HighExcellentNoneCabinets, doors, furniture

Multi-Room Planner

Add all the rooms in your project to get a combined paint estimate. Enter net paintable area for each room (use the Calculator tab to find each room's area).

Prep Work Checklist

Professionals spend 60-70% of their time on prep. Check off each step before you open a can.

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How to Use This Calculator

1

Enter Room Dimensions

Input the length, width, and height of your room. For multiple rooms, calculate each separately and add the totals.

2

Subtract Openings

Enter the number and size of doors and windows to exclude their area from the paint calculation.

3

Get Gallons Needed

See the total paintable area and the number of gallons required, accounting for the number of coats and paint coverage rate.

Formula & Methodology

Wall Area

Wall Area = 2 × (Length + Width) × Height

Calculates the total area of all four walls in a rectangular room.

Paintable Area

Paintable = Wall Area − Door Area − Window Area

Subtracts openings that do not receive paint.

Gallons Needed

Gallons = (Paintable Area × Coats) / Coverage per Gallon

Standard latex paint covers approximately 350-400 sq ft per gallon on smooth surfaces.

About this calculation · Accuracy & Methodology

Key Terms

Coverage Rate
The area one gallon of paint will cover on a smooth surface — typically 350-400 sq ft. Rough or textured surfaces reduce coverage by 20-30%.
Primer
A preparatory coating applied before paint to seal porous surfaces, improve adhesion, and block stains. Essential for bare drywall and drastic color changes.
Sheen
The level of glossiness in a paint finish. Flat/matte hides imperfections; satin and semi-gloss are easier to clean; high-gloss is used for trim and doors.
Mil Thickness
A unit of paint film thickness equal to 0.001 inches. Most paints dry to 1.0-1.5 mils per coat.
Touch-Up
Keeping leftover paint for future repairs. Label the can with the room, color name, and date for easy identification.

Real-World Examples

Example 1

Standard Bedroom

Room: 12ft × 14ft × 8ft, 1 door (21 sq ft), 2 windows (24 sq ft total), 2 coats

Result: Wall area = 416 sq ft, minus openings = 371 sq ft. At 2 coats, you need 742 sq ft of coverage. At 350 sq ft/gallon, purchase 3 gallons.

Example 2

Open-Plan Living Area

Room: 20ft × 25ft × 9ft, 2 doors (42 sq ft), 5 windows (75 sq ft), 2 coats

Result: Wall area = 810 sq ft, minus openings = 693 sq ft. At 2 coats, you need 1,386 sq ft of coverage. Purchase 4 gallons.

Paint Finish Guide

FinishSheen LevelDurabilityBest For
Flat / Matte0-5%LowCeilings, low-traffic rooms
Eggshell10-25%MediumLiving rooms, bedrooms
Satin25-35%Medium-HighKitchens, hallways
Semi-Gloss35-70%HighBathrooms, trim, doors
High-Gloss70-85%Very HighCabinets, furniture

Getting Professional Results from Your Paint Job

Prep Work Is Everything

Professional painters spend 60-70% of their time on preparation. Fill nail holes with spackle, sand smooth, clean walls with a damp cloth, and tape edges carefully. A well-prepped surface means fewer coats, better adhesion, and a finish that lasts years longer than paint applied over dust and imperfections.

How Many Coats Do You Really Need?

Two coats is the standard for most color changes. A single coat often looks uneven and lets the old color bleed through. When making a dramatic change (dark to light or light to dark), use a tinted primer first to reduce the need for a third coat of expensive finish paint.

How to Use This Calculator

  1. 1
    Measure Wall Areas

    Calculate total wall area by multiplying room perimeter by ceiling height, or enter individual wall dimensions.

  2. 2
    Subtract Doors and Windows

    Deduct the area of each door (~20 sq ft) and window (~15 sq ft) to get the net paintable surface area.

  3. 3
    Enter Number of Coats

    Standard painting requires 2 coats. Drastic color changes (dark to light) may need 3 coats; touching up may need only 1.

  4. 4
    Choose Coverage per Gallon

    Most interior paints cover 350-400 sq ft per gallon. Textured walls, rough surfaces, or primer may cover less (250-300 sq ft).

  5. 5
    Get Gallons Needed

    The calculator shows total gallons required rounded up to the nearest quart or gallon for practical purchasing.

Key Formulas

Wall AreaArea = Perimeter x Height
Net Paintable AreaNet = Gross Area - Doors/Windows
Gallons NeededGallons = Net Area x Coats / Coverage
Typical Coverage~350 sq ft per gallon (smooth walls)

Key Terms

Coverage Rate — The square footage one gallon of paint covers in a single coat. Typically 350-400 sq ft for interior latex on smooth surfaces.
Coats — The number of paint layers applied. Two coats provide full hide and color depth; more may be needed for dramatic color changes.
Primer — A preparatory base coat that seals the surface, improves adhesion, and provides uniform porosity for better topcoat coverage.
Sheen (Flat/Eggshell/Satin/Gloss) — The reflectivity level of the dried paint. Higher sheen is more durable and washable; flat hides surface imperfections best.
Trim Paint — Paint formulated for doors, window casings, and baseboards. Usually semi-gloss or gloss for durability and easy cleaning.
VOC — Volatile Organic Compounds in paint that evaporate and cause odor and air quality concerns. Low-VOC and zero-VOC paints are safer for interior use.

Frequently Asked Questions

Do I always need a primer coat?

Primer is essential when painting over bare drywall, raw wood, stains, dark colors, or glossy surfaces. When repainting a wall with a similar color in good condition, a high-quality paint-and-primer-in-one product may suffice. Skipping primer on bare surfaces typically requires an extra topcoat to achieve uniform coverage.

Why do I need more paint when going from dark to light colors?

Dark pigments show through light paint because light colors have less hiding power. Going from deep navy to off-white may require 3 or even 4 coats without a gray primer blocking the dark base. Using a tinted primer (tinted halfway between the old and new color) significantly reduces the number of topcoats needed.

Does rolling waste more paint than spraying?

Actually, spraying wastes more paint -- typically 20-30% is lost to overspray, even with careful masking. Roller application is the most efficient method for walls, with minimal waste. Brushes are efficient for trim but slow for large surfaces. Sprayers offer the smoothest finish on furniture or cabinets but require more prep and cleanup.

Is ceiling paint different from wall paint?

Yes. Ceiling paint is thicker to reduce drips when applied overhead and has a flat sheen that minimizes shadows from surface imperfections. It also typically has more hiding power per coat. While you can use wall paint on ceilings in a pinch, dedicated ceiling paint makes the job easier and produces a better result.