Paint Square Footage Calculator

Estimate the total square footage of walls you need to paint and how much paint you'll need for your project.

Room Dimensions

Enter the length and height for each wall. If you have fewer than four walls, leave the extra fields blank or enter '0'.

Wall 1 Length (feet):

Wall 1 Height (feet):

Wall 2 Length (feet):

Wall 2 Height (feet):

Wall 3 Length (feet):

Wall 3 Height (feet):

Wall 4 Length (feet):

Wall 4 Height (feet):

Obstructions (Doors & Windows)

Enter the number and average dimensions of doors and windows to subtract their area from the total.

Number of Doors:

Door Width (feet):

Door Height (feet):

Number of Windows:

Window Width (feet):

Window Height (feet):

Paint Details

Number of Paint Coats:

Paint Coverage per Gallon (sq ft):

Calculation Results:

Total Wall Area: 0 sq ft

Total Obstruction Area: 0 sq ft

Net Paintable Area: 0 sq ft

Total Area to Cover (with coats): 0 sq ft

Estimated Gallons of Paint Needed: 0 gallons

function calculatePaintSquareFootage() { // Get wall dimensions var wall1Length = parseFloat(document.getElementById('wall1Length').value) || 0; var wall1Height = parseFloat(document.getElementById('wall1Height').value) || 0; var wall2Length = parseFloat(document.getElementById('wall2Length').value) || 0; var wall2Height = parseFloat(document.getElementById('wall2Height').value) || 0; var wall3Length = parseFloat(document.getElementById('wall3Length').value) || 0; var wall3Height = parseFloat(document.getElementById('wall3Height').value) || 0; var wall4Length = parseFloat(document.getElementById('wall4Length').value) || 0; var wall4Height = parseFloat(document.getElementById('wall4Height').value) || 0; // Get obstruction dimensions var numDoors = parseFloat(document.getElementById('numDoors').value) || 0; var doorWidth = parseFloat(document.getElementById('doorWidth').value) || 0; var doorHeight = parseFloat(document.getElementById('doorHeight').value) || 0; var numWindows = parseFloat(document.getElementById('numWindows').value) || 0; var windowWidth = parseFloat(document.getElementById('windowWidth').value) || 0; var windowHeight = parseFloat(document.getElementById('windowHeight').value) || 0; // Get paint details var numCoats = parseFloat(document.getElementById('numCoats').value) || 1; // Default to 1 coat if invalid var paintCoverage = parseFloat(document.getElementById('paintCoverage').value) || 350; // Default to 350 sq ft/gallon // Ensure non-negative values for dimensions and counts wall1Length = Math.max(0, wall1Length); wall1Height = Math.max(0, wall1Height); wall2Length = Math.max(0, wall2Length); wall2Height = Math.max(0, wall2Height); wall3Length = Math.max(0, wall3Length); wall3Height = Math.max(0, wall3Height); wall4Length = Math.max(0, wall4Length); wall4Height = Math.max(0, wall4Height); numDoors = Math.max(0, numDoors); doorWidth = Math.max(0, doorWidth); doorHeight = Math.max(0, doorHeight); numWindows = Math.max(0, numWindows); windowWidth = Math.max(0, windowWidth); windowHeight = Math.max(0, windowHeight); numCoats = Math.max(1, numCoats); // At least 1 coat paintCoverage = Math.max(1, paintCoverage); // At least 1 sq ft/gallon // Calculate total wall area var totalWallArea = (wall1Length * wall1Height) + (wall2Length * wall2Height) + (wall3Length * wall3Height) + (wall4Length * wall4Height); // Calculate total obstruction area var totalDoorArea = numDoors * doorWidth * doorHeight; var totalWindowArea = numWindows * windowWidth * windowHeight; var totalObstructionArea = totalDoorArea + totalWindowArea; // Calculate net paintable area (subtract obstructions) var netPaintableArea = totalWallArea – totalObstructionArea; if (netPaintableArea < 0) { netPaintableArea = 0; // Cannot have negative paintable area } // Calculate total area to cover considering multiple coats var totalAreaToCover = netPaintableArea * numCoats; // Calculate estimated gallons of paint needed var gallonsNeeded = totalAreaToCover / paintCoverage; // Display results document.getElementById('totalWallArea').innerText = totalWallArea.toFixed(2); document.getElementById('totalObstructionArea').innerText = totalObstructionArea.toFixed(2); document.getElementById('netPaintableArea').innerText = netPaintableArea.toFixed(2); document.getElementById('totalAreaToCover').innerText = totalAreaToCover.toFixed(2); document.getElementById('gallonsNeeded').innerText = gallonsNeeded.toFixed(2); } // Run calculation on page load with default values window.onload = calculatePaintSquareFootage;

Understanding Your Paint Square Footage

Painting a room can be a rewarding DIY project, but accurately estimating the amount of paint needed is crucial to avoid multiple trips to the store or excessive waste. Our Paint Square Footage Calculator helps you determine the exact surface area of your walls, taking into account doors and windows, and then estimates the number of paint gallons required.

Why Calculate Paint Square Footage?

Budgeting: Paint can be expensive. Knowing how much you need helps you budget accurately and avoid overspending.
Efficiency: Prevents buying too little paint, which can lead to delays if you run out mid-project, especially if your specific color isn't readily available.
Waste Reduction: Avoids buying too much paint, which can be costly and leave you with excess cans to store or dispose of.
Consistent Finish: Ensures you have enough paint from the same batch, preventing slight color variations that can occur between different paint batches.

How to Measure for Accurate Results

To get the most accurate results from the calculator, follow these simple measuring steps:

Measure Each Wall: Use a tape measure to find the length and height of each wall you plan to paint. Even if walls appear to be the same size, slight differences can add up. Input these values into the "Room Dimensions" section.
Measure Doors: For each door, measure its width and height. If you have multiple doors of varying sizes, calculate the area for each and sum them, or use an average size for simplicity if the differences are minor. Input the total number of doors and their average dimensions.
Measure Windows: Similarly, measure the width and height of each window. Again, you can average sizes if they are similar. Input the total number of windows and their average dimensions.
Consider Obstructions: The calculator automatically subtracts the area of doors and windows. For other significant unpaintable areas like large built-in shelves or fireplaces, you might need to manually subtract their area from the "Net Paintable Area" result.
Determine Number of Coats: Most painting projects require two coats for optimal coverage and color depth. If you're painting over a dark color with a light one, or if the surface is porous, you might need a primer and potentially more coats.
Check Paint Coverage: Look at the paint can label for the "coverage rate," usually expressed in square feet per gallon (e.g., 350-400 sq ft/gallon). This value can vary based on paint type and quality.

Example Calculation:

Let's say you have a room with two walls that are 12 feet long and 8 feet high, and two walls that are 10 feet long and 8 feet high. The room has one door (3 feet wide, 7 feet high) and two windows (3 feet wide, 4 feet high). You plan to apply two coats of paint, and your chosen paint covers 350 square feet per gallon.

Wall 1 Area: 12 ft * 8 ft = 96 sq ft
Wall 2 Area: 12 ft * 8 ft = 96 sq ft
Wall 3 Area: 10 ft * 8 ft = 80 sq ft
Wall 4 Area: 10 ft * 8 ft = 80 sq ft
Total Wall Area: 96 + 96 + 80 + 80 = 352 sq ft
Door Area: 1 door * 3 ft * 7 ft = 21 sq ft
Window Area: 2 windows * 3 ft * 4 ft = 24 sq ft
Total Obstruction Area: 21 + 24 = 45 sq ft
Net Paintable Area: 352 sq ft – 45 sq ft = 307 sq ft
Total Area to Cover (2 coats): 307 sq ft * 2 = 614 sq ft
Estimated Gallons Needed: 614 sq ft / 350 sq ft/gallon = 1.75 gallons

Based on this, you would likely need to purchase two gallons of paint to complete the project, allowing for a small buffer.

Tips for Your Painting Project:

Buy a Little Extra: It's always a good idea to buy slightly more paint than the calculator suggests (e.g., round up to the next full gallon). This accounts for minor spills, touch-ups, or unexpected surface absorption.
Consider Surface Texture: Rough or highly textured surfaces (like stucco or heavily textured drywall) will absorb more paint and may require more gallons than smooth surfaces.
Primer Use: If you're painting over a very dark color with a light one, or if the surface is new or unpainted, using a primer can reduce the number of paint coats needed and improve adhesion.
Ceilings and Trim: Remember that this calculator is primarily for walls. If you're also painting ceilings or trim, you'll need to calculate those areas separately.

By using this calculator and following these tips, you can approach your painting project with confidence, knowing you have the right amount of paint for a beautiful finish.