How much area does one gallon of paint cover?

On average, one gallon of paint will cover about 400 square feet with one coat. This can vary based on the texture of the surface and the quality of the paint. This calculator uses 400 sq ft per gallon as a standard.

Do I need to subtract the area of doors and windows?

Yes, for an accurate estimate. Our calculator automatically subtracts a standard area for each door (21 sq ft) and window (15 sq ft) you specify, so you don't buy paint for areas you won't be painting.

How many coats of paint do I need?

Typically, you will need two coats of paint, especially if you are painting over a darker color. If you are using a high-quality paint and primer in one, or painting over a similar light color, you might be able to get away with one coat.

Paint Calculator | How Much Paint Do I Need?

How Does This Work?

This calculator estimates your paint needs by calculating the total paintable area of your room.

Wall Area: First, it calculates the total surface area of the walls using the formula: 2 × (Length + Width) × Height.
Ceiling Area: If you choose to paint the ceiling, it adds the ceiling area: Length × Width.
Deductions: To give you a more accurate estimate, the calculator automatically subtracts a standard area for each door (21 sq ft) and window (15 sq ft) you specify.
Total Paint Needed: Finally, it divides the total paintable area by the average coverage of a gallon of paint (400 sq ft) and multiplies by the number of coats you plan to apply. This gives you the total gallons of paint required.

The Surprising History of Paint

Paint is one of humanity's oldest inventions, with cave paintings dating back over 40,000 years. Early paints were made from simple, natural materials: crushed minerals like ochre (for reds and yellows) and charcoal (for black), mixed with a binder like animal fat, saliva, or egg yolk.

The first major innovation came much later. In 1867, a patent was granted to a company called Sherwin-Williams for the first ready-to-use, pre-mixed paint in a resealable tin can. Before this, painters had to buy pigments and binders separately and mix them on-site, a messy and inconsistent process. This invention revolutionized the industry, making painting accessible, consistent, and much easier for both professionals and homeowners. It democratized color and interior design in a way that was previously unimaginable.

Explore More Related Tools

While you're here, check out some of our other popular construction and math calculators:

Square Footage Calculator: The first step before calculating paint needs.
Concrete Calculator: For projects involving concrete work.
Unit Converter: Essential for converting project measurements.
Fraction Calculator: Handle fractional inches with ease.
Loan Calculator: Planning the finances for a renovation.
Percentage Calculator: For calculating material overages or budget contingencies.
Scientific Calculator: For advanced calculations.
Age Calculator: Find the time between two dates.
Time Card Calculator: Track labor hours for your project.
Time Zone Converter: Coordinate with suppliers or contractors.

Frequently Asked Questions (FAQ)

How much should I add for waste?

It's a good rule of thumb to buy about 10-15% more paint than calculated. This extra paint covers mistakes, spills, touch-ups, and ensures you have a small amount left over for future scuffs and scratches.

Does the texture of the wall affect how much paint I need?

Yes, significantly. Rough, textured surfaces (like stucco or "popcorn" ceilings) have more surface area and will absorb more paint than smooth drywall. For highly textured surfaces, you may need up to 25% more paint than the calculator estimates.

What if I'm only painting one wall?

You can still use this calculator. Simply enter the length of the wall you are painting in the "Room Length" field, and enter '0' for the "Room Width" field. This will calculate the area for that single wall.

Paint Calculator

You will need approximately: