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Paint Calculator — How Much Paint Do I Need? (2026)

3 verified sources|Last verified 2026-03-30

What you need to know

Paint is one of the most cost-effective home improvement projects — a single room typically costs $200-$500 in materials for a DIY job or $300-$800 with a professional painter. The key to staying on budget is knowing exactly how much paint you need before you buy. Most homeowners overbuy by 20-30%, wasting $25-$70 per extra gallon.

This calculator uses industry-standard coverage rates (350-400 square feet per gallon) to determine exactly how many gallons you need based on your room dimensions, number of coats, and whether you're priming. It accounts for windows and doors — areas you don't need to paint — to prevent overbuying.

The biggest cost variable is paint quality. Budget interior latex paint costs $25-$40 per gallon and may need 3 coats for full coverage. Premium paint from Benjamin Moore or Sherwin-Williams costs $50-$70 per gallon but typically covers in 1-2 coats — often making premium paint cheaper per project despite the higher per-gallon price. If you're planning a larger renovation, our home affordability calculator can help you budget across multiple projects.

Whether you're refreshing a single room or painting an entire house, accurate measurement is the foundation of an on-budget project. Enter your room dimensions below and we'll calculate exactly what you need — gallons of paint, primer, and estimated total cost based on your paint quality selection.

How paint costs break down

A typical interior paint job has three cost components. Understanding each helps you budget accurately and decide between DIY and hiring a professional.

**Paint: $25-$70 per gallon.** Standard latex interior paint costs $25-$40 per gallon at retailers like Home Depot and Lowe's. Premium brands (Benjamin Moore, Sherwin-Williams) run $50-$70 per gallon. One gallon covers approximately 350-400 square feet with one coat — most rooms need two coats for proper coverage.

**Primer: $15-$30 per gallon.** Primer is essential when painting over dark colors, new drywall, or stained surfaces. A gallon of primer covers 300-400 square feet. Skipping primer often means needing an extra coat of paint, which costs more in the long run.

**Supplies: $30-$80.** Brushes ($5-$15 each), rollers and covers ($10-$20), painter's tape ($5-$10 per roll), drop cloths ($10-$20), and a paint tray ($5-$10). If hiring a professional, labor runs $2-$6 per square foot depending on your area.

**Labor (if hiring): $200-$500 per room.** Professional painters charge $25-$50 per hour or $2-$6 per square foot of wall area. A standard 12x12 room takes a professional 4-6 hours including prep, painting, and cleanup. Most professionals include paint in their quote at a markup of 20-40% over retail — ask for an itemized estimate to compare.

What affects your paint cost

Five factors determine your total paint cost. Each one can double or halve your budget.

**1. Room size and ceiling height.** More wall area means more paint. Standard 8-foot ceilings are straightforward, but 10-foot or vaulted ceilings increase wall area by 25% or more. Our calculator accounts for this automatically when you enter room dimensions.

**2. Number of coats.** Most interior paint jobs require two coats for even coverage. If you're painting over a similar color, one coat may suffice. Dark-to-light color changes may need primer plus two coats — effectively three layers.

**3. Paint quality.** Budget paint ($25/gallon) requires more coats and fades faster. Premium paint ($50-$70/gallon) covers in fewer coats and lasts 7-10 years. The per-gallon cost difference often evens out when you factor in fewer coats needed. See our home affordability calculator for broader home budgeting. If you're deciding between DIY and hiring, our rent vs buy calculator can help you understand your overall housing budget.

**4. Surface condition.** Walls with holes, cracks, or peeling paint need prep work (spackle, sanding, priming) that adds time and materials. New drywall always needs primer.

**5. DIY vs. professional.** DIY costs $200-$500 per room in materials. Professional painters charge $300-$800 per room including materials and labor. The gap narrows for large or complex rooms where professional speed saves significant time.

Ways to save on your paint project

Small decisions can cut your paint budget by 30-50% without sacrificing quality.

**Buy during sales.** Major retailers run paint sales 4-6 times per year, typically around holidays (Memorial Day, Labor Day, Black Friday). Savings of 25-40% per gallon are common.

**Measure accurately.** Overbuying paint is the most common waste. This calculator helps you determine exactly how many gallons you need based on your room dimensions and number of coats. Subtract window and door areas to avoid buying excess.

**Use quality paint in fewer coats.** A premium paint at $50/gallon that covers in one coat costs less than a budget paint at $25/gallon that needs three coats. Total coverage cost: $50 vs $75 — and premium paint lasts longer.

**Prep walls yourself, hire for painting.** If hiring a professional, doing your own prep work (taping, covering furniture, filling holes, sanding) can reduce labor costs by 20-30%. Learn more about how we calculate paint coverage.

For more about our methodology and data sources, visit our data sources page. If painting is part of preparing your home for sale, our home affordability calculator can help the next buyer.

**Test before committing.** Buy a sample quart ($8-$12) and paint a 2x2 foot section on the wall before buying full gallons. Colors look different on walls than on swatches due to lighting, adjacent colors, and surface texture. This $10 test can save you $100+ in wrong-color paint returns.

How we calculate this

This calculator estimates paint quantity and cost using industry-standard coverage rates from major paint manufacturers. The formula divides your total wall area by the coverage rate per gallon (350-400 square feet for standard interior latex paint) and multiplies by the number of coats you plan to apply.

Wall area is calculated as: perimeter × wall height, minus window and door areas. Standard windows are estimated at 15 square feet and standard doors at 20 square feet. The calculator subtracts these automatically when you specify the number of windows and doors in the room.

Paint cost is calculated by multiplying the gallons needed by the per-gallon price for your selected quality tier. We round up to whole gallons since paint is sold in full gallons. Primer is estimated separately at 300-350 square feet per gallon coverage. Cost data is sourced from current retail pricing at national home improvement retailers.

Key takeaways

  • One gallon of paint covers 350-400 square feet depending on quality — a standard 12x12 room needs about 2 gallons for two coats.
  • Two coats is the standard recommendation for most projects — one coat rarely provides full coverage, and three coats is only needed for dramatic color changes.
  • Premium paint costs more per gallon but covers more area and lasts 2-3x longer than economy paint, often making it cheaper over the life of the room.
  • Always subtract doors (21 sq ft each) and windows (15 sq ft each) from your wall area to avoid over-buying.
  • This estimate covers paint only — budget an additional $20-50 for primer (if needed), painter's tape, drop cloths, rollers, and brushes.
Step 1 of 3

What room are you painting?

Pick a common room size or enter your own dimensions.

Quick select

Don't have a tape measure? One walking pace ≈ 2.5 feet.

Standard ceiling height is 8 feet. Older homes may be 9-10 feet.

Frequently Asked Questions

How much paint do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings has about 384 square feet of wall space. After subtracting a door (21 sq ft) and two windows (30 sq ft), you have about 333 paintable square feet. At standard coverage (375 sq ft/gallon), you need about 1 gallon per coat, or 2 gallons for the recommended 2 coats. Buy an extra quart for touch-ups. Our calculator subtracts window and door areas from your total wall area to prevent overbuying. Standard windows are approximately 15 square feet and standard doors are 20 square feet.
How many square feet does a gallon of paint cover?
A gallon of paint covers approximately 350-400 square feet on smooth walls with a single coat. Economy paints average 350 sq ft/gallon, while premium paints with higher pigment concentration can cover up to 400 sq ft/gallon. Textured walls, bare drywall, or porous surfaces reduce coverage by 10-20%. Our calculator subtracts window and door areas from your total wall area to prevent overbuying. Standard windows are approximately 15 square feet and standard doors are 20 square feet.
Do I need 1 or 2 coats of paint?
Two coats is the standard recommendation for most interior paint jobs. One coat may suffice if you're repainting the same color or using a paint-and-primer-in-one over a well-primed surface. Use 3 coats when painting a light color over a very dark wall, or when using a lower-quality paint. Our calculator subtracts window and door areas from your total wall area to prevent overbuying. Standard windows are approximately 15 square feet and standard doors are 20 square feet.
Is expensive paint worth it?
Generally yes. Premium paints ($60-80/gallon) contain more pigment and better binders, meaning better coverage per coat, superior durability (10-15 years vs 5-7 for economy), easier application, and better washability. You may save money on labor since fewer coats are needed. For high-traffic areas like kitchens and hallways, premium paint pays for itself in longevity.
How much does it cost to paint a room professionally?
Professional interior painting typically costs $2-6 per square foot of wall space, or $400-1,800 for a standard 12x12 room. This includes labor, paint, primer, and supplies. Cost varies by region, wall condition, ceiling height, and paint quality. The national average is about $1,000 per room. DIY painting costs $50-150 for the same room (paint and supplies only). Always test paint samples on your actual walls before committing to full gallons.

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Data sources

See an error in this data? Let us knowAbout our data sources and methodologyEditorial standards