Exterior paint answer guide

How much exterior paint do I need?

Estimate exterior paint and primer gallons from house dimensions, stories, gables, openings, coats, surface condition, and waste.

Reviewed - July 16, 2026

Short answer

Estimate exterior paintable area from the outside wall perimeter, wall height, story count, and any gables. Subtract the window and door area you do not intend to paint, multiply the remaining area by the number of finish coats, add waste, and divide by the selected paint coverage per gallon.

The exterior paint calculator follows that method and separately shows paintable area, finish paint, primer, DIY materials, labor, and a directional contractor total. It can use either house dimensions or a measured net exterior area.

Treat the result as a purchasing plan, not a surface-repair diagnosis. Extensive scraping, lead-safe work, rot, specialty coatings, lifts, and unusual access need separate assessment and quotes.

Use the exterior paint calculator

Exterior paint quantity formula

For dimension mode, calculate the exterior wall area as 2 x (length + width) x wall height x story count.
Add each triangular gable as gable width x gable height / 2.
Subtract the combined area of windows, doors, and other openings you will not paint to get net paintable area.
Use measured net exterior area directly when a takeoff, contractor, or plan already provides it.
Multiply net paintable area by the number of finish coats, then add the calculator's waste allowance for cut-in, texture, overspray, and touch-ups.
Divide the waste-adjusted finish area by the current coverage-per-gallon assumption and round up to a practical purchase quantity.
If primer is selected, calculate one additional waste-adjusted primer coat over the net paintable area.

Quick examples

24 ft by 20 ft one-story home

4.2 gal

8 ft walls, no gables, 140 sq ft openings, 2 finish coats

40 ft by 28 ft two-story home

17.1 gal

9 ft walls, two gables, 260 sq ft openings, primer and 2 finish coats

32 ft by 26 ft three-story home

22.0 gal

9 ft walls, one gable, 220 sq ft openings, 2 finish coats

2,400 sq ft measured exterior area

17.6 gal

Known net paintable area, primer and 2 finish coats

1,200 sq ft repaint with one coat

4.4 gal

Known net paintable area, no primer, maintenance repaint

These generated examples use the current regional coverage and waste assumptions. The selected paint grade, coat count, primer, condition, and access affect the material and cost cards.

Worked example

40 ft by 28 ft two story home with 9 ft walls.

Paintable exterior area

2,328 sq ft

2,588 sq ft gross less 260 sq ft openings

Exterior paint

17.1 gal

standard paint, 2 coats, 10% waste

Primer

8.6 gal

One primer coat with the same waste buffer

DIY materials

$1,329–$2,474

Paint, prep materials, primer if selected, and supplies

Starter shopping list

standard exterior paint 17.1 gal
Exterior primer 8.6 gal
Caulk, patching compound, sanding and masking supplies weathered prep allowance
Rollers, brushes, trays, drop cloths and cleanup supplies 1 project kit allowance

This example is generated from the same calculator logic used on the Exterior house paint calculator page.

Measure exterior surfaces, not floor area

Walk the house and record outside length, width, wall height, story count, and separate gables before estimating gallons.
Break bump-outs, dormers, attached garages, porches, and detached structures into separate rectangles or use known-area mode when you have a detailed takeoff.

Openings, coats, and primer

Subtract only openings that will not receive paint; include trim, fascia, doors, shutters, or soffits separately when they use another product or sheen.
Choose the actual finish-coat count and add primer for bare, repaired, stained, porous, or major color-change surfaces when the product system calls for it.

Prep and access change the plan

Washing, scraping, sanding, caulking, masking, and spot repair often take longer than rolling the finish coat.
Upper stories, sloped sites, roofs, landscaping, and poor weather access can change labor and equipment needs without changing the gallon count.

Buy and store consistently

Confirm coverage, recommended film build, primer compatibility, and container sizes on the exact product data sheet before buying.
Keep labeled touch-up paint and record the product, sheen, color, and batch details after the project is complete.

Common mistakes

Using the house footprint or interior floor area as the exterior paintable area.
Forgetting gables, trim, attached sections, or surfaces that use a different coating system.
Subtracting all openings but then overlooking paintable door frames, trim, or fascia.
Buying for one coat when the product, color change, or surface condition needs primer and two finish coats.
Assuming the gallon estimate includes repair, lead-safe procedures, lifts, scaffolding, or specialty coatings.

FAQ

How do I calculate exterior paint for a house?

Measure the exterior wall perimeter, wall height, story count, gables, and paintable openings. Calculate net exterior wall area, multiply by coats, add waste, and divide by the paint's coverage per gallon.

Should I subtract windows and doors from exterior paint area?

Yes, when those surfaces will not be painted. Keep trim, frames, doors, shutters, fascia, soffits, and other painted details in separate estimates if they use another product, color, or sheen.

How many coats of exterior paint should I estimate?

Use the coat count specified by the paint system and surface condition. A maintenance repaint may use one finish coat, while color changes, repairs, porous surfaces, and many manufacturer systems need primer and two finish coats.

Does the calculator include primer?

Turn on primer to add one waste-adjusted primer coat over the net exterior paintable area. Confirm whether the chosen product system requires full priming, spot priming, or neither.

Can I use known exterior square footage instead of house dimensions?

Yes. Known-area mode is useful when a drawing, contractor takeoff, or careful measurement already provides net paintable exterior square footage.

Does this include a contractor's exterior painting price?

The calculator shows a directional labor and contractor-total range based on the selected region, stories, and surface condition. It does not replace bids for repairs, lead-safe work, equipment, unusual access, or specialty coatings.