Paint calculator: gallons and cost
One gallon of paint covers about 350 square feet per coat, and contractor-grade interior product costs $34 to $52 a gallon in 2026. This calculator takes your wall area and coat count, figures gallons of paint and primer, and prices labor at $0.75 to $1.50 per square foot per coat. Two coats is the honest default for a color change.
Worked example: 1,500 sq ft wall area, 2 coats coats
That takes 9 gallons (Paint needed). National-average costs:
| Line | Quantity | Cost range |
|---|---|---|
| Interior paint | 9 gallons | $306 to $468 |
| Primer | 4 gallons | $88 to $136 |
| Prep and painting labor | 3,000 sq ft per coat | $2,250 to $4,500 |
| Tape, plastic, caulk, patch compound and roller covers | 10% | $39 to $60 |
| Estimated total | $2,683 to $5,164 |
Enter the paintable wall area and how many coats the job needs. The interactive calculator on this page recomputes these numbers for your dimensions and adjusts for any US state.
How to measure for painting work
Figure the wall area
Walk each room and multiply the perimeter by the ceiling height. A 12 by 14 room with 9 foot ceilings is 52 feet of perimeter times 9, or 468 square feet of wall. Add the rooms up and you have the number this calculator wants.
Deduct only the big openings
Subtract patio doors, open archways and full-height glass. Leave standard windows and doors in the count, since cutting around them takes the time the missing footage would have saved.
Set the coat count honestly
Same color refresh is one coat. Any color change is two. Dark to light or covering red is a tinted primer plus two finish coats, and bidding it at two straight coats is how painters lose a day per room.
Price ceilings as their own line
Ceilings run at the floor area in flat paint and go faster per foot than walls, but they are a neck-and-shoulders job with different product. Keep them out of the wall number and quote them separately.
What this calculator assumes
- Numbers are national averages for an interior repaint in an occupied home with standard prep.
- The total covers wall paint by the gallon, one pass of primer over patches and color changes, and labor per coat.
- The 10 percent allowance covers tape, plastic, caulk, patch compound and roller covers.
- Ceilings, trim, doors and cabinets are separate scopes and are not in this number.
- Heavy drywall repair, wallpaper removal, and walls over 10 feet price above the high end.
- Vacant houses spray faster and can come in under the low end on big footage.
Cost factors in painting work
Surface condition
Nail pops, tape cracks, water stains and kid damage all get fixed before the first cut line. Prep can be 10 minutes a room or two hours a room, and it is the least visible, most underbid part of the trade.
Color change
Staying in the same family means two easy coats. Dark over light or light over dark means a tinted primer first, and reds and deep blues are famous for needing a third finish coat to hold.
Height and layout
Stairwells, two-story foyers and vaulted great rooms need plank setups or ladders on stairs. The footage is the same, the ladder handling is not, and open floor plans add miles of cut line where walls meet ceilings.
Occupied versus vacant
Furniture moving, floor protection and working around a family slow everything down. A vacant repaint with sprayed walls can run twice as fast as the same footage occupied.
Product grade
Contractor-grade interior runs $145 to $225 per 5 gallon bucket, and premium retail lines can double the per-gallon cost. On a whole-house repaint that choice alone swings the material line by hundreds.
Frequently asked questions
How much paint do I need per square foot?
Figure one gallon per 350 square feet per coat on smooth walls. So 1,500 square feet of wall at two coats is 3,000 coat-feet, which is 8.6 gallons, and you buy 9. Rough texture and unpainted drywall drink more, closer to 300 square feet per gallon.
How many coats does a repaint need?
Two coats for any color change, and most manufacturers require two for the warranty. One coat only works as a refresh in the same color and sheen. Going from dark to light usually takes a tinted primer plus two coats, so bid three passes on those walls.
What does interior painting cost per square foot in 2026?
Installed pricing for walls at two coats runs $1.75 to $3.50 per square foot of wall area nationally. Material is only 15 to 25 percent of that. The rest is prep, cutting, rolling and the second trip around the room, which is why labor drives every paint bid.
Do I subtract windows and doors from wall area?
Measure perimeter times ceiling height and only deduct big openings like patio sliders and open archways. Standard windows and doors wash out, because the brush time to cut around them costs about what the skipped square footage saves.
How much does Staxen cost for painters?
The price is $59 per month per AI employee, $149 per month for all three. Eddie the Estimator turns your room measurements into a priced proposal from a voice note, and Ivy the Invoicer chases the final payment so you do not have to. First job free, no card needed.
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