Purdy Calculator

Professional Purdy Painting Calculator

Calculate surface area and paint requirements for a professional finish.

1 Coat 2 Coats (Recommended) 3 Coats

Project Estimates

Total Net Wall Area: 0 sq. ft.

Paint Required: 0 Gallons

Estimated Labor Time: 0 Hours

*Estimation based on 350 sq. ft. coverage per gallon and standard professional application rates.

function calculatePurdyCoverage() { var length = parseFloat(document.getElementById('purdy_length').value) || 0; var width = parseFloat(document.getElementById('purdy_width').value) || 0; var height = parseFloat(document.getElementById('purdy_height').value) || 0; var coats = parseFloat(document.getElementById('purdy_coats').value) || 1; var doors = parseFloat(document.getElementById('purdy_doors').value) || 0; var windows = parseFloat(document.getElementById('purdy_windows').value) || 0; // Gross wall area var grossArea = 2 * (length + width) * height; // Deductions (Average door is 21 sq ft, average window is 15 sq ft) var deductions = (doors * 21) + (windows * 15); var netArea = grossArea – deductions; if (netArea < 0) netArea = 0; // Coverage rate: 350 sq ft per gallon is the industry standard for professional tools var totalSurfaceToPaint = netArea * coats; var gallonsNeeded = totalSurfaceToPaint / 350; // Labor estimate: Pro rate approx 100-150 sq ft per hour including prep var hoursNeeded = totalSurfaceToPaint / 100; document.getElementById('res_area').innerText = netArea.toLocaleString(); document.getElementById('res_gallons').innerText = gallonsNeeded.toFixed(2); document.getElementById('res_hours').innerText = hoursNeeded.toFixed(1); document.getElementById('purdy_results').style.display = 'block'; }

Understanding the Purdy Calculation Method

Achieving a professional-grade finish requires more than just high-quality brushes and rollers; it requires precision in project planning. The Purdy Calculator is designed to provide professional painters and DIY enthusiasts with accurate estimates for wall surface area, paint volume, and time management.

How to Calculate Wall Surface Area

To determine the total area of your project, use the following logic:

• Gross Area: Multiply the perimeter of the room (2 x (Length + Width)) by the wall height.
• Deductions: Subtract the area of openings. A standard door is typically 21 square feet, while a standard window averages 15 square feet.
• Net Area: This is your actual painting surface.

Estimating Paint Volume

Standard architectural coatings generally cover 350 to 400 square feet per gallon. However, professional results almost always require two coats for proper hide and durability. Our calculator uses a conservative 350 sq. ft. per gallon coverage rate to ensure you never run out of material mid-stroke, which is critical for maintaining a "wet edge" and avoiding lap marks.

Professional Efficiency Examples

Room Size	Net Surface Area	Paint (2 Coats)
Small Bathroom (6'x8'x8′)	~190 sq. ft.	1.1 Gallons
Standard Bedroom (12'x12'x8′)	~330 sq. ft.	1.9 Gallons
Large Living Area (20'x15'x10′)	~650 sq. ft.	3.7 Gallons

Pro Tips for Using Purdy Tools

When using high-capacity tools like Purdy Colossus™ rollers or Marathon™ sleeves, remember that tool loading affects your coverage. Proper technique ensures the paint is distributed evenly across the calculated square footage. Always account for a 10% waste factor for textured surfaces like knockdown or stucco, as the increased surface area of the texture requires significantly more material than a smooth drywall finish.