Interior Painting Cost Calculator

What does an interior painting cost calculator measure?

An interior painting cost calculator estimates paint gallons and total cost for a room. It uses the room size, wall height, openings, coats, paint coverage, paint price, supplies, and labor rate.

Paint prices and labor rates change by brand, finish, location, and contractor. This calculator asks you to enter your own prices, so the result matches the numbers you are actually seeing.

The result includes paint, supplies, and optional labor. If you are doing the work yourself, leave the labor rate at 0.

How is interior painting cost calculated?

The wall area is:

Wall area = 2 x (room length + room width) x wall height

If you include the ceiling, the calculator adds:

Ceiling area = room length x room width

Then it subtracts openings and multiplies by coats:

Coat area = paintable area x number of coats

Gallons are rounded up:

Gallons = coat area / coverage per gallon

The total cost is:

Total cost = paint cost + supplies cost + labor cost

Labor cost uses the painted square footage and the rate you enter.

How to use this interior painting cost calculator

1. Enter the room length, width, and wall height.
2. Choose whether to include the ceiling.
3. Enter the door and window area to subtract.
4. Enter the number of coats and coverage per gallon.
5. Enter your paint price, supplies, and labor rate.
6. Read the gallon count and cost breakdown.

If the paint can lists its own coverage, use that number. Behr says one gallon of interior paint covers about 250 to 400 sq ft for one coat.

Example: painting a 12 ft by 12 ft room

Say a room is 12 ft long, 12 ft wide, and 8 ft high. The wall area is:

2 x (12 + 12) x 8 = 384 sq ft

If you subtract 40 sq ft for doors and windows:

384 - 40 = 344 sq ft

With 2 coats:

344 x 2 = 688 sq ft of coat area

At 350 sq ft per gallon:

688 / 350 = 1.97 gallons

The calculator rounds up to 2 gallons. At $45 per gallon, paint costs $90. If supplies are $60 and labor is $2 per painted sq ft, the estimate is $838.

Paint coverage and cost inputs

Use this table as a check on the fields. Your product label and quote should win over any general estimate.

Dark color changes, raw drywall, repairs, texture, or stains can reduce coverage. Primer may also be needed, but this calculator treats primer as a separate supply cost.

Safety note for older homes

EPA says homes built before 1978 are more likely to have lead-based paint. That matters if you sand, scrape, repair, or disturb old paint before painting.

If your home may have lead paint, read EPA guidance before starting. A simple paint estimate is not a safety plan.

If you are estimating a room before finishing walls, use the Drywall Calculator first. For block walls, use the Concrete Block Calculator. You can also browse all Home Improvement calculators.

Limitations

This calculator estimates cost from the inputs you enter. It does not know your exact paint brand, wall texture, primer needs, trim, repairs, furniture moving, travel fees, or contractor minimums.

For a hired project, use this result as a planning number. A real quote can change after a painter sees the room.