ToolwickInterior Painting Cost Calculator
Use this free interior painting cost calculator to estimate the paint, primer, supplies and labor needed to repaint one room or a whole house. Enter your room size and finish choices to get a total with a likely range, gallons rounded up to whole cans, and a DIY-versus-professional comparison.
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How to Use This Interior Painting Cost Calculator
Enter the length, width and ceiling height of a room in feet, then the number of doors and windows. Pick the number of coats, the paint quality, and whether to include the ceiling, trim and primer, then say whether you are painting it yourself or hiring a pro. Press Calculate to see the total, a line-by-line breakdown and a comparison across paint tiers. For rooms of different sizes, run the calculator once per room and add the totals.
Why This Matters
Paint is one of the cheapest ways to change a home, but quotes vary widely and the job is easy to misjudge. A 12 × 14 ft bedroom with 8 ft ceilings has roughly 350–400 sq ft of wall. A professional commonly charges a few hundred to a thousand dollars for it, while the same room done yourself often costs $150–$250 in materials. Knowing the numbers lets you check a contractor's bid against a realistic baseline, decide whether the savings are worth a couple of weekends, and avoid the classic second trip to the store for one more gallon.
Homeowners use an estimate before listing a house, since fresh neutral paint is one of the most common pre-sale updates. Landlords use it between tenants, and renters use it to judge what a fair repaint charge looks like. Whole-house projects add up fast: ten rooms at $800 each is $8,000, and a $10-per-gallon difference across 30 gallons is another $300 before labor enters the picture. A few minutes here helps you set a budget before you call anyone.
How It's Calculated
The calculator measures each surface, converts it to gallons, then prices materials and labor:
Perimeter = 2 × (length + width)
Gross walls = perimeter × ceiling height
Openings = doors × 21 sq ft + windows × 15 sq ft
Paintable wall = gross walls − openings
Ceiling = length × width
Trim area = (perimeter − 3 ft × doors) × 0.5 ft
+ 4 sq ft × (doors + windows)
Gallons = round up (area × coats ÷ 350)
Primer gallons = round up (wall + ceiling ÷ 300)
Pro labor = area × rate × coat factor × prep factor
Paint prices are $28, $42 and $65 per gallon for economy, standard and premium. Trim paint adds $10 per gallon for semi-gloss, and primer is $26 per gallon. Coat factors are 0.65 for one coat, 1.0 for two and 1.3 for three. Prep factors are 1.00, 1.15 and 1.35. Trim labor is $1.75 per linear foot of baseboard, plus $35 per door and $25 per window. Priming labor is 35% of your rate. The range shown is −10% to +15% of the total.
To stay on the safe side, gallons are always rounded up to whole cans, and walls, ceiling and trim are bought separately even if you use the same color. The 350 sq ft per gallon figure is a conservative rule of thumb; many labels claim up to 400, but textured or porous walls use more. Prices are typical assumptions, and local prices vary.
Worked Example
Take a 14 × 12 ft bedroom with 8 ft ceilings, one door and two windows. It gets two coats of standard paint on walls and ceiling, hired out at $1.25 per sq ft with good wall condition. These are the tool's default settings.
- Perimeter: 2 × (14 + 12) = 52 ft, so gross walls are 52 × 8 = 416 sq ft.
- Openings: 21 + 2 × 15 = 51 sq ft, leaving 365 sq ft of paintable wall. The ceiling is 14 × 12 = 168 sq ft.
- Wall paint: 365 × 2 ÷ 350 = 2.09, rounded up to 3 gallons × $42 = $126.
- Ceiling paint: 168 × 2 ÷ 350 = 0.96, rounded up to 1 gallon × $42 = $42.
- Labor: (365 + 168) × $1.25 × 1.0 × 1.0 = $666.25.
- Total: $126 + $42 + $666.25 = $834.25. The range is about $751–$959, or $4.97 per sq ft of floor.
Switch to DIY and the same room costs $168 in paint plus a $50 supplies allowance, or $218.
Tips & Common Mistakes
- Measure, don't guess. Measure each room with a tape. Being off by 2 ft on a side changes wall area by about 30 sq ft.
- Budget for two coats. One coat rarely hides the old color evenly. Going from dark to light usually needs primer plus two finish coats.
- Buy a little extra. Keep a partial can for touch-ups. Mixing a new batch later can give a slightly different shade.
- Compare quotes line by line. Ask what each bid includes: prep, patching, furniture moving, ceilings, trim and number of coats.
- Test older homes for lead. In a pre-1978 home, sanding or scraping can release lead dust. Test first and use a contractor certified under the EPA lead-safe rules if lead is present.
Frequently Asked Questions
How much does it cost to paint a room?
A professionally painted average bedroom commonly runs from a few hundred to around $1,000, depending on local labor rates and prep. DIY materials for the same room are often $150–$250. Use the calculator with your own dimensions for a closer figure.
How much paint do I need for a 12x12 room?
With 8 ft ceilings, one door and two windows, you have about 333 sq ft of wall. Two coats need about 666 sq ft of coverage, so plan on 2 gallons for the walls. The ceiling adds roughly 1 more gallon for two coats.
Is it cheaper to paint a room yourself?
Yes, usually by 60–80%, because labor is most of a professional bill. The trade-off is your time, the need for ladders and supplies, and a less even finish if you are inexperienced. High ceilings, stairwells and heavy repairs are often worth hiring out.
Do I need primer?
Prime new drywall, patched areas, stains and big color changes, such as dark to light. If you are repainting a clean wall in a similar color, a good paint alone is usually enough. Tick the primer box to see the added cost.
How many coats of paint do I need?
Two coats is the standard for an even, durable finish. One coat can work over a similar color with premium paint. Three coats may be needed for deep reds, dark colors or a dramatic change.
Does this estimate include wallpaper removal or furniture moving?
No. It covers paint, primer, supplies and standard painting labor with the prep level you choose. Wallpaper removal, major drywall repair, cabinets, popcorn ceiling removal and lead abatement are separate costs. This is a planning estimate, not a contractor's bid.