How to Estimate an Exterior Painting Job: Formula and Example

Exterior painting estimates go wrong in two places: measuring floor area instead of wall area, and forgetting prep time. This guide fixes both. (For interior jobs, see how painters estimate a job.)

Step 1: Measure the walls

Perimeter × average wall height. A house with a 160 ft perimeter and 18 ft walls: 160 × 18 = 2,880 sq ft. Add gable triangles separately (½ × base × height) if they're large.

Step 2: Subtract openings

Subtract large doors, windows and garage doors. If they total 300 sq ft: 2,880 − 300 = 2,580 sq ft of paintable wall.

Step 3: Calculate paint

Two coats: 2,580 × 2 = 5,160 sq ft of coverage. At about 350 sq ft per gallon (check the product's data sheet — rough siding covers less): 5,160 ÷ 350 = 14.7, so 15 gallons. Add primer for bare wood and repairs — say 3 gallons.

Step 4: Calculate labor

If your crew brushes and rolls about 150 sq ft per hour per coat: 5,160 ÷ 150 = 34.4 hours. Add prep — washing, scraping, caulking, masking — say 16 hours. Total: 50.4 hours.

Step 5: Price it

The rates below are example numbers to show the math. Use your own supplier prices, labor costs and local permit fees.

Line item	Quantity	Rate	Amount
Labor (prep + 2 coats)	50.4 hrs	$55/hr	$2,772
Exterior paint	15 gal	$60/gal	$900
Primer	3 gal	$40/gal	$120
Caulk, tape, plastic, sundries	Allowance	—	$200
Subtotal			$3,992
Overhead & profit (25% markup)			$998
Total			$4,990

Step 6: Write what's included

List the surfaces (siding, trim, fascia, doors), the number of coats, the product line, and what's excluded (rotten wood replacement, lead-safe work on pre-1978 homes unless priced). Clear scope is what gets a painting proposal signed quickly.

Send it before you leave

Once your numbers are set, the fastest way to win the job is to get the proposal in front of the customer while they're still thinking about it. With Quote Commander you can build the line items on site, text or email the proposal, and let the customer sign and pay a deposit from their phone. See how it works for painters, or read how to set your markup.

Frequently asked questions

How many gallons of paint does it take to paint a house exterior?

Divide the paintable wall area by the coverage on the can (often 250–400 sq ft per gallon), then multiply by the number of coats. A 2,580 sq ft house at two coats and 350 sq ft per gallon needs about 15 gallons.

Should I measure floor area or wall area for exterior painting?

Wall area. Use perimeter times wall height, then subtract large openings.

How do I price prep work?

Estimate prep as separate hours — washing, scraping, sanding, caulking and masking — rather than hiding it in a per-square-foot rate.