How to Estimate Painting Jobs: Interior and Exterior Formulas That Win Bids

Every painting job you win or lose starts with an estimate. Bid too high and you lose the job; bid too low and you win it and lose money. The fix is a repeatable method based on measured surfaces and production rates, not on how big the room looks. Here is a method you can use for both interior and exterior work.

The estimate formula

Price = labour + materials + overhead + profit

• Labour = hours to prep, paint and clean up × loaded labour rate
• Materials = paint, primer, caulk, tape, plastic, sundries
• Overhead = a share of vehicle, insurance, software, marketing and office time
• Profit = a target percentage on top, commonly 15 to 25 percent for residential repaint

Step 1: Measure paintable area

Walls: perimeter of the room × ceiling height, minus large openings.

Example: a 12 × 14 foot bedroom with 8-foot ceilings. Perimeter = 52 feet. 52 × 8 = 416 square feet. Subtract one door (about 20 square feet) and one window (about 15 square feet) = 381 square feet of wall.

Ceilings: length × width = 168 square feet.

Trim: measure baseboard and casing in linear feet. Doors and windows are usually counted as units.

For exteriors, measure each wall's width and height, add gables (width × height ÷ 2), and record siding type, trim lengths, fascia, soffits, doors, shutters and the height of the work, which drives ladder and safety time.

Step 2: Calculate paint quantity

Gallons = area × coats ÷ coverage per gallon

Smooth interior walls often cover 350 to 400 square feet per gallon per coat; rough or porous surfaces cover less. Check the product data sheet.

Bedroom walls: 381 × 2 coats ÷ 375 = 2.03 gallons. Add 10 percent and round up: 3 gallons (or a gallon plus a two-gallon option, depending on how you buy). Ceiling: 168 × 2 ÷ 375 = 0.9, so 1 gallon.

Premium paint costs more per gallon but often covers better and lasts longer. Show the difference in your proposal rather than defaulting to cheap paint.

Step 3: Estimate labour with production rates

Production rate is how much surface a painter covers per hour for a given task. Track your own numbers; until you have them, use conservative starting points like these for interior repaint with brush and roller:

Prep is separate. Moving furniture, covering floors, patching, sanding, caulking and priming can take as long as painting on older homes. Estimate it as its own line.

Bedroom labour example:

• Prep: 2 hours
• Walls: 381 sq ft × 2 coats ÷ 200 per hour = 3.8 hours
• Ceiling: 168 × 2 ÷ 160 = 2.1 hours
• Baseboards: 52 ft ÷ 60 = 0.9 hours
• One door and frame: 1 hour
• Clean-up: 0.75 hours
• Total: about 10.5 hours

Step 4: Apply your loaded labour rate

Your loaded rate is the hourly wage plus payroll taxes, workers' compensation and other labour burden. If you pay a painter $24 per hour and burden adds 25 percent, the loaded rate is $30. If you paint alone, use the hourly wage you want to earn plus self-employment taxes and benefits.

Bedroom labour: 10.5 hours × $30 = $315

Step 5: Add materials, overhead and profit

• Paint: 4 gallons × $50 = $200
• Sundries (tape, plastic, caulk, patch, rollers): $35
• Materials subtotal: $235, plus 10 to 20 percent markup for handling = $270
• Overhead: many small companies allocate 15 to 25 percent of job cost; at 20 percent of ($315 + $270) = $117
• Subtotal: $702
• Profit at 20 percent: $702 ÷ 0.80 = about $880

That is a realistic price for a fully prepped bedroom with walls, ceiling, trim and a door using quality paint in many markets. If it seems high compared with local bids, remember that many low bids skip prep, use cheaper paint or omit insurance.

Exterior estimates: extra factors

• Access: two-storey work, steep grades and landscaping slow production. Add ladder or lift time.
• Surface condition: scraping, sanding, wood repair and priming bare spots can dominate labour.
• Weather days: build schedule buffers; many paints need minimum temperatures and dry conditions.
• Lead paint: homes built before 1978 may contain lead-based paint. If you disturb painted surfaces in those homes, the EPA RRP Rule requires firm certification, a certified renovator and lead-safe practices. Budget the extra containment and clean-up time.

Present it as good, better, best

Offer three options:

1. Good: walls only, standard paint, minimal prep.
2. Better: walls, ceilings and trim, premium paint, full prep.
3. Best: everything in Better plus doors, minor drywall repair and an extended warranty.

Options shift the conversation from "is this too expensive?" to "which option fits me?", and many clients choose the middle.

Track actuals to improve every estimate

After every job, record estimated versus actual hours and materials. After 10 jobs, your production rates will be far more accurate than any table. This is the habit that separates profitable painting companies from busy ones.

Mistakes to avoid

1. Estimating by "looks like a day". Measure every time.
2. Ignoring prep. It is where bids are won or lost on older homes.
3. Using one production rate for every surface. Ceilings, trim and textured walls are slower.
4. No written scope. List rooms, surfaces, coats, products and what is excluded.

Insurance, licensing and your overhead rate

Your overhead percentage should come from real numbers, not a guess. Add up a year of non-job costs: vehicle, insurance, phone, software, marketing, accounting, licences, and your own time spent estimating and managing. Divide by the year's expected job costs (labour plus materials). If overhead is $40,000 and you expect $200,000 of job costs, your overhead rate is 20 percent.

Insurance is part of that overhead and differs from trade to trade. Painters typically need general liability, commercial auto and, once you have employees, workers' compensation. Many homeowners and every commercial client will ask for a certificate of insurance. Some states require a contractor or home improvement licence for painting jobs above a dollar threshold, and cities may require a business licence. Check before you bid, because the cost of compliance belongs in your price.

Commercial and new-construction estimates

Commercial repaints and new-construction work follow the same logic but at a different scale:

• Take-offs from plans. You measure surfaces from drawings and specifications rather than on site.
• Specified products and systems. The spec book often dictates primer, coats and sheen; price exactly what is specified.
• Production rates rise on large open walls with sprayers, but access, protection and scheduling constraints (night work, occupied buildings) slow it down.
• Payment terms are slower and may include retainage held back until completion. Price for the cash-flow cost.

Start with small commercial work, such as offices and retail units, before bidding large projects. A few accurate small bids teach you more than one big loss.

Your next step

Measure one room in your own home and run it through the formula. Then time yourself painting it. That single exercise gives you your first real production rate.

The full guide, Starting a Residential & Commercial Painting Business, includes estimating worksheets, proposal templates, RRP compliance steps, crew management checklists and a 30/60/90-day launch plan for $0.99.