Don't Buy Too Much: The Ultimate Paint Estimator
Painting is the most popular DIY home improvement project, but buying the paint is often the most confusing part. High-quality interior paint now costs over $60 per gallon. Buy too little, and you are stuck with unmatched dye lots; buy too much, and you waste money. Our Advanced Paint Calculator takes the guesswork out of the aisle. It calculates the precise surface area of your walls, subtracts the windows and doors, and adjusts for surface texture to tell you exactly how many gallons and quarts you need.
The "350 Rule" (Paint Coverage)
To use this calculator effectively, it helps to understand the industry standard. On average, one gallon of paint covers 350 to 400 square feet (single coat). However, this number assumes a perfectly smooth, primed wall. Real-world conditions often require more.
Factors That Change Your Paint Needs
Our tool asks about "Surface Texture" for a reason. Different walls absorb paint differently:
- Smooth Drywall: Standard coverage (350-400 sq ft/gal).
- Textured / Stucco: Rough surfaces have more surface area than flat ones. They can absorb 20-30% more paint.
- Fresh (Unpainted) Drywall: New drywall acts like a sponge. The first coat (or primer coat) will soak in rapidly, significantly reducing your coverage rate.
Do I Really Need 2 Coats?
In 90% of cases, Yes. Even "One-Coat Guaranteed" paints often require touch-ups.
- Going Darker: If you are painting a light wall a dark color (e.g., Navy Blue over White), you might need 3 coats to get full saturation.
- Going Lighter: If you are painting a dark wall a light color (e.g., White over Red), you definitely need a high-quality primer plus 2 coats of topcoat.
Don't Forget the "Fifth Wall" (Ceilings)
Beginners often forget to calculate the ceiling. Ceiling paint is usually cheaper and flatter than wall paint (to hide imperfections). If you toggle "Paint Ceiling?" in our calculator, we add the floor area (Length × Width) to your total, assuming a standard flat white paint.
Frequently Asked Questions
How much paint do I need for trim?
Trim (baseboards, door frames, window casings) typically requires a different sheen (Semi-Gloss or Satin). A good rule of thumb is 1 gallon of trim paint for every 6-8 gallons of wall paint. Our calculator provides a specific estimate for trim if selected.
What happens if I don't subtract windows?
Professional estimators often don't subtract windows and doors. They treat that extra calculated area as their "wastage buffer" for spills, roller absorption, and clean-up. If you have standard-sized windows, you can leave them in to ensure you have leftover paint for future touch-ups.
What is the difference between Satin and Eggshell?
Flat/Matte: No shine. Hides bumps best but hard to clean. Best for ceilings.
Eggshell: Low luster. Good for living rooms.
Satin: Medium sheen. Easier to clean. Best for hallways and kids' rooms.
Semi-Gloss: Shiny and durable. Best for trim and bathrooms.