How to Calculate Price Per Square Foot for House Painting

Nothing gives a house a fresh look like a new coat of paint. Whether you're doing the painting yourself or hiring someone to do it for you, knowing how to calculate price per square foot for house painting is a helpful way to estimate costs and compare quotes. Calculating per square foot can also help do-it-yourself painters buy the right amount of paint for the job.

Steps

1. Factor in the price of paint and materials when you calculate for house painting.
   
   • Include materials for preparing, mixing, applying and cleaning up paint in house painting costs.
   • Professional house painting costs also include labor.
2. Estimate the amount of paint, with a gallon of primer, or base paint, covering 330 square feet and a gallon of other paint providing coverage up to 350 square feet.
   
   • The composition of base paint is different, which is why it covers fewer square feet per gallon.
   • Paint costs can range from $15 to $60 per gallon. Designer and specialty paint can increase house painting costs even more.
3. Figure the cost per square foot of a professional's flat fee by dividing the cost by the square footage.
   
   • For example, an $800 estimate for 1,500 square feet would be 800 divided by 1,500 which is equal to a 53.3 cent cost per square foot.
4. Determine exterior square feet by multiplying the height times the width of each exterior wall.
5. Add the square footage of each of the exterior walls together to find the sum total.

exterior Painting

1. Calculate for house painting by multiplying the length by width of the room or rooms that you want to paint.
   
   • Add the individual sums together.
2. Measure the height and width of each door and each window in a room to be painted.
   
   • Multiply height by width to find the square footage of each door and window.
   • Combine the totals for each door and window to calculate for house painting.
   • Subtract the door/window total from the room square footage for house painting costs.
   • The average window is 16 square feet and the average door is 21 square feet. When a window or door is slightly smaller, multiply the total by .80. If larger, multiply by 1.5.
3. Decide if you will also be painting the ceiling.
   
   • Find square footage by multiplying two adjacent sides.
   • Ceilings tend to take up to 85% more paint, particularly acoustical and popcorn ceilings.

Spray Painting

1. Reduce the cost per square foot by spray painting large paint jobs.
   
   • Small jobs aren't economical when you factor in the cost of a sprayer, which can cost hundreds of dollars.
2. Consider the transfer efficiency of spray painting equipment when you calculate for house painting with spraying.
   
   • Spray painting tends to only get a portion of the total paint on the intended surface. The remainder ends up in the sprayer's exhaust filters or on the floor.
   • Transfer efficiency is the total paint sprayed divided by the paint that reaches the surface.
3. Multiply the cost per foot by the transfer efficiency percentage to reach a more accurate calculation per square foot.

Warnings

• Indoor textured walls require more paint than smooth walls.

Sources and Citations

• http://www.pprc.org/pubs/factsheets/coatcost.html
• http://homeguides.sfgate.com/calculate-price-per-square-foot-house-painting-8718.html
• http://www.csgnetwork.com/roompaintcalc.html
• http://www.paintingnetworx.com/info/painting-cost-per-square-foot/

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