How much paint do I need for a room?

Calculate wall area (height × perimeter of the room), subtract window and door area (approximately 20 sq ft each), then divide by 350 (sq ft per gallon). Multiply by the number of coats — typically 2 for most interior projects. For example, a 12×12 bedroom with 8-foot ceilings has roughly 384 sq ft of wall area. Divided by 350 and multiplied by 2 coats = 2.2 gallons. Round up to 3 gallons to account for waste and touch-ups.

How many square feet does a gallon of paint cover?

Most interior paints cover 350–400 square feet per gallon per coat. Rough or porous surfaces (unprimed drywall, textured ceilings, brick) absorb more paint and may only yield 250–300 sq ft per gallon. High-quality paints with more pigment and solids content tend to cover closer to 400 sq ft per gallon. Always add 10% to your calculated quantity as a buffer for touch-ups and uneven application.

Do I need primer, and does it count toward my paint calculation?

Primer is separate from your topcoat paint calculation. You need primer when painting over raw drywall, dark colors, stains, or glossy surfaces. Calculate primer coverage using the same formula (350 sq ft per gallon), but you typically only need one coat of primer before two coats of paint. Self-priming or paint-and-primer-in-one products eliminate the separate primer step but may still require two coats for complete coverage over dramatic color changes.

How much does it cost to buy paint for a room?

Paint costs $25–$35/gallon for budget options, $40–$60/gallon for mid-range quality, and $65–$100/gallon for premium brands. For a typical 12×12 bedroom requiring 3 gallons, expect to pay $75–$105 for budget paint, $120–$180 for mid-range, or $195–$300 for premium. For a whole house (2,000 sq ft interior walls), total paint cost typically runs $400–$1,200 depending on quality tier.

How Much Paint Do I Need? — 2026 Calculator Guide

One gallon of paint covers approximately 350–400 square feet per coat. For a standard 12×12 bedroom with 8-foot ceilings, you need about 2–3 gallons for two coats. Use this formula: (total wall area in sq ft × number of coats) ÷ 350 = gallons needed. Add 10% for waste and touch-ups, then round up to the nearest whole gallon.

The Paint Calculation Formula

$$\text{Gallons needed} = \frac{\text{Wall area (sq ft)} \times \text{Number of coats}}{350} \times 1.10$$

Step 1 — Calculate wall area: Add up all four walls: (Wall 1 length + Wall 2 length + Wall 3 length + Wall 4 length) × wall height

Step 2 — Subtract doors and windows: Subtract approximately 20 sq ft per standard door, 15 sq ft per standard window

Step 3 — Divide by 350, multiply by coats: Most projects require 2 coats. First-time painting over dark colors may need 3.

Step 4 — Add 10% buffer: Multiply result by 1.10 for touch-ups and uneven coverage

Step 5 — Round up to whole gallons: Paint is sold in quarts (0.25 gal), gallons, and 5-gallon buckets. Always round up.

Room-by-Room Paint Estimate

Room	Typical Size	Wall Area (approx)	2 Coats	Paint Needed
Small bedroom	10×10, 8-ft ceilings	320 sq ft	640 sq ft	2 gallons
Standard bedroom	12×12, 8-ft ceilings	384 sq ft	768 sq ft	2.5 → 3 gallons
Master bedroom	14×16, 9-ft ceilings	540 sq ft	1,080 sq ft	3.5 → 4 gallons
Small bathroom	6×8, 8-ft ceilings	224 sq ft	448 sq ft	1.5 → 2 gallons
Kitchen	10×12, 9-ft ceilings	396 sq ft	792 sq ft	2.5 → 3 gallons
Living room	15×20, 9-ft ceilings	630 sq ft	1,260 sq ft	4 → 5 gallons
Dining room	12×14, 9-ft ceilings	468 sq ft	936 sq ft	3 gallons
Open floor plan (living/dining)	20×25, 9-ft ceilings	810 sq ft	1,620 sq ft	5 → 6 gallons

Wall area approximations account for one door and one to two windows per room. Actual results vary.

Ceiling Paint Calculation

Ceilings are calculated separately using a simpler formula:

$$\text{Ceiling gallons} = \frac{\text{Room length} \times \text{Room width}}{350}$$

Ceilings typically only need one coat if you use flat ceiling paint and are re-coating a white ceiling. First-time coating or color change requires two coats.

Example — 15×20 living room ceiling: (15 × 20) = 300 sq ft ÷ 350 = 0.86 gallons → buy 1 gallon for one coat, 2 gallons for two coats.

Trim Paint — How Much You Need

Trim (baseboards, door frames, window casings, crown molding) is typically painted with semi-gloss or gloss paint. Calculate trim paint by linear footage:

A quart of trim paint covers approximately 100–125 linear feet with one coat
A standard room has roughly 50–75 linear feet of trim (baseboards + door/window casings)
Rule of thumb: 1 quart per average-sized room; buy an extra quart for touch-ups on a multi-room project

How Surface Type Affects Coverage

Surface Type	Coverage Per Gallon	Adjustment Needed
Smooth, previously painted drywall	380–400 sq ft	None — full coverage
Primed new drywall	350–375 sq ft	Standard calculation
Unprimed new drywall	200–300 sq ft	Must prime first
Rough/textured walls (orange peel, skip trowel)	300–350 sq ft	Add 10%–15%
Brick or masonry (interior)	150–200 sq ft	Add 30%–50%
Smooth wood paneling	300–350 sq ft	Add 10%
Dark color going light	May need extra coat	Budget for 3 coats

Paint Sheen Guide — Flat vs. Eggshell vs. Semi-Gloss

Sheen	Coverage Per Gallon	Best For	Washability
Flat / Matte	350–400 sq ft	Ceilings, low-traffic rooms	Low — marks hard to wipe
Eggshell	350–400 sq ft	Bedrooms, living rooms	Medium — wipes clean
Satin	350–400 sq ft	Kitchens, hallways	Good — handles moisture
Semi-gloss	300–350 sq ft	Trim, bathrooms, kitchens	Excellent — scrub-able
High-gloss	275–325 sq ft	Cabinets, trim highlights	Best — very durable

Glossier paints cover slightly less per gallon because they’re applied thinner for a smoother finish.

Paint Cost by Quality Tier

Quality Tier	Price Per Gallon	Examples
Budget	$25–$35	Contractor-grade flat paint, Glidden interior
Mid-range	$40–$60	Behr Premium (Home Depot), Valspar Signature
Premium	$65–$85	Benjamin Moore Regal Select, Sherwin-Williams Emerald
Ultra-premium	$85–$100	Farrow & Ball, Fine Paints of Europe

Total Project Cost Example — 3-Bedroom House

A typical 3-bedroom, 2-bath home with approximately 1,800 sq ft of interior wall space (excluding ceilings and trim):

Item	Quantity	Mid-Range Paint ($50/gal)	Premium Paint ($75/gal)
Interior wall paint	12 gallons (2 coats)	$600	$900
Ceiling paint	4 gallons (1 coat)	$160	$280
Trim paint	2 quarts + 1 gallon	$75	$125
Primer	4 gallons (if needed)	$120	$160
Total paint cost		$955	$1,465

Excludes labor. Professional painter labor typically adds $2–$6 per sq ft.

Written by WealthVieu

WealthVieu researches and writes data-driven personal finance guides using primary sources including the IRS, Bureau of Labor Statistics, Federal Reserve, and Census Bureau.

The content on Wealthvieu is for informational purposes only and should not be considered financial, tax, or investment advice. Consult a qualified professional before making financial decisions. Full disclaimer · Editorial policy