How to Estimate a Painting Job (Square Footage, Coats & Prep)

Most painters lose money not on paint but on under-pricing the part the client never sees: patching, sanding, taping, and masking. A good painting estimate starts from measured square footage, decides coats and coverage, then prices prep and labor honestly. Do it in that order and you stop eyeballing a number that leaves your prep work unpaid.

1. Measure the surfaces in square footage

For interior work, measure each wall (length × height) and each ceiling (length × width), then add them up by room. Don't subtract small openings like doors and standard windows — the cutting-in around them eats the time you'd save — but do subtract large openings like a wall of glass. For exterior work, measure each face of the building and treat trim, fascia, and soffits as their own line because they paint far slower than open wall.

• Group by room or elevation so the estimate reads clearly and you can adjust one area without redoing the rest.
• Measure trim, doors, and windows separately — they're priced by the unit or the hour, not by wall area.
• Note the existing condition (bare drywall, glossy, dark color) now — it decides primer and coats.

2. Decide coats and account for coverage

One gallon of interior paint covers roughly 350–400 square feet per coat on smooth, sealed surface — less on texture or porous drywall. Two finish coats is the standard for a quality result, and you'll add a primer coat over bare drywall, stains, or a big color change. Multiply your square footage by the number of coats, divide by the coverage rate, and round up to whole gallons so you're never short mid-wall.

3. Quantify paint and materials from the area

Once you have square footage and coats, the materials list is arithmetic. Convert area to gallons of finish and primer, then add the consumables every job burns through. Build it once as a template and reuse it — the line items rarely change from job to job, only the quantities do.

• Finish paint: (area × coats) ÷ ~375 sq ft/gal, rounded up to whole gallons.
• Primer: by the area that actually needs it, not the whole job.
• Supplies: rollers, brushes, tape, plastic, drop cloths, and filler as a lot.
• Sundries for exterior: caulk, patching compound, and any specialty primer.

4. Price the prep — it's most of the labor

Prep is where painting estimates go wrong. Patching nail holes and cracks, sanding, caulking gaps, taping, and masking floors and fixtures can be half the labor on a repaint and more on a neglected or exterior surface. Price prep as its own line by the hour so it's visible and paid, rather than burying it in a per-square-foot rate that assumes the walls are perfect. Walls that need heavy patching or peeling-paint scraping should carry a higher prep number, and you should say so to the client.

5. Add labor, then mark up materials

Price application labor by area for open walls and ceilings at your loaded rate, and by the hour for trim, doors, and windows, which go far slower per square foot. Then mark up your materials to cover pickup, the partial gallons you can't reuse, and sourcing time. The paint is a small share of the job, so a consistent materials markup matters less here than pricing labor and prep correctly — but apply it anyway so nothing leaks.

6. A worked example: repainting an interior

Picture a repaint with about 4,500 square feet of wall and ceiling to cover in two coats. That's roughly 24 gallons of finish before primer, plus primer for the patched and color-change areas. Lay it out in three sections — prep, materials, and labor — and the totals follow once you set your own gallon price, prep hours, and labor rate. The numbers below are structure, not a quote.

• Prep: patch and sand + tape and mask, priced by the hour.
• Materials: finish paint (gallons), primer, and supplies as a lot.
• Labor: walls and ceilings by area + trim, doors, and windows by the hour.
• Then: apply your markup, fold in your contractor fee, and add tax for your jurisdiction.

7. Present it like a pro and send it fast

A clean, sectioned estimate that separates prep from painting tells the homeowner you've thought the job through — and it protects you when they ask why your number is higher than the painter who 'just rolls the walls.' Group the work, take a deposit, and send a branded PDF the same day. Bill-The-Job computes every total exactly and converts the accepted estimate into an invoice in one tap.

Work in your language, bill in your client's

Plenty of contractors run the whole job in one language and have a client who reads another — a Spanish-speaking crew and an English-speaking homeowner, or a Spanish-speaking owner and an English-speaking GC. You shouldn't have to choose. Write the estimate in the language you think in, then hand the client a clean document in theirs — English or Spanish — with every quantity, unit price, and total carried across unchanged. The language gets translated; the numbers never do.