Paint Calculator
Calculate paint calculator gallons square feet. Precise material estimations for building contractors and DIY home builders across USA/UK/Canada.
Calculate Paint Calculator
Enter project dimensions below to compute required material quantities.
Calculation Results
Calculated using verified construction formula: Paint Gallons = ( ( (2 * (Length + Width) * Height) - Openings ) * Coats ) / 350 sq ft per gallon
Quick Summary
The Paint Calculator computes interior wall paint gallons, 1-coat primer gallons, net wall square footage, quart equivalents, and material costs for 1, 2, or 3-coat paint jobs.
- Net Wall Area Deductions: Subtracts doors (21 sq ft each) and windows (15 sq ft each) from gross wall area.
- Coats & Primer Scoping: Calculates 2-coat paint finish gallons and 1-coat drywall primer gallons.
- Coverage Density Standard: Uses 350 sq ft per gallon standard interior paint coverage.
How to Use the Paint Calculator
- Enter Room Length in feet.
- Enter Room Width in feet.
- Enter Ceiling Height in feet.
- Select Number of Coats (2 coats standard).
- Click Calculate to view paint gallons, primer gallons, net wall area, and paint cost.
Paint Calculator Formula & Method
This tool utilizes verified construction geometric formulas to compute material requirements:
Net Wall Area = Gross Wall Area - Openings (50 sq ft default)
Paint Gallons = Math.ceil((Net Wall Area * Coats) / 350 sq ft per gallon)
Where:
- 350 Sq Ft per Gallon: Standard coverage yield for premium interior latex acrylic wall paint.
- Primer Coat: Specialized base coat sealed over raw drywall mud to ensure uniform sheen.
- 2-Coat Standard: Two topcoats required for true color depth and washability.
Worked Example
Example: 20ft * 15ft Room with 8ft Ceiling (2 Coats Interior Paint)
- Gross Wall Area: 2 * (20 + 15) * 8 = 560 sq ft
- Net Wall Area (minus 50 sq ft openings): 560 - 50 = 510 sq ft
- 2-Coat Total Coverage Area: 510 * 2 = 1,020 Sq Ft
Applying the formula yields:
Total Paint Gallons Needed: 1,020 / 350 = 2.91 -> 3 Gallons
Primer Gallons Needed: 510 / 400 = 2 Gallons
Estimated Paint Cost: 3 * = .00
What This Calculator Includes vs. Does Not Include
What This Calculator Includes
- Interior Wall Paint & Primer Engineering: Measures latex acrylic paint, PVA wall primer, net square footage, and quart options.
- Standard Opening Deductions: Automatically deducts doors and windows from paint coverage calculations.
What This Calculator Does Not Include
- Painter Masking Tape & Plastic Drop Cloths: Painter masking tape rolls.
Tips & Best Practices
- Always Buy 2 Coats of Paint for Color Changes: Applying 2 coats guarantees complete hide and prevents patchy streaks, even when using paint-and-primer-in-one products.
- Pour Paint Cans Into a 5-Gallon Bucket (Box Paint): Mix multiple 1-gallon cans together in a 5-gallon bucket before painting to ensure seamless color consistency.
Common Mistakes to Avoid
- Painting Over Unprimed Drywall Mud: Painting directly over fresh drywall mud without PVA primer causes flashing where joint mud absorbs paint duller than surrounding paper.
Frequently Asked Questions (FAQ)
How many gallons of paint do I need for a 20x15 room?
A 20x15 room with 8ft ceilings (510 net sq ft) requires 3 gallons of interior paint for 2 coats.
How many square feet does 1 gallon of paint cover?
One gallon of interior wall paint covers 350 to 400 square feet with a single coat.
How much wall area do doors and windows subtract?
Subtract 21 sq ft for each standard interior door and 15 sq ft for each standard window.
Do I need 1 coat or 2 coats of paint?
Two coats are recommended for all wall color changes to achieve rich color depth, uniform sheen, and durability.
How much does a gallon of interior paint cost?
Quality interior latex wall paint costs between and per gallon.
How much primer do I need for fresh drywall?
One gallon of PVA drywall primer covers 400 sq ft (2 gallons for a 20x15 room).
How long should I wait between coats of interior paint?
Wait 2 to 4 hours between coats for latex water-based interior paint.
How many quarts in a gallon of paint?
There are 4 quarts in 1 gallon of paint.
Is this paint calculator free to use?
Yes, TibCal's Paint Calculator is 100% free.