Paint calculator
Estimate paintable wall area, ceiling and trim options, gallons, primer, material cost, labor range, and a basic shopping list.
Home Project Estimates
Paint calculator
May 9, 2026
12 ft by 14 ft room, 8 ft walls, 2 coats.
Shopping list
- standard interior latex paint2.2 gal
- Primer1.1 gal
- Roller covers, tray, brush, tape, drop clothBasic kit
Assumptions
- 350 sq ft per 1.0 gal coverage
- 10% waste buffer
- 21 sq ft per door and 15 sq ft per window deducted
- U.S. near average; pricing data: U.S. near average pricing
Planning estimate only. Not a contractor quote, engineering advice, or permit review.
Calculator setup
12 ft by 14 ft room, 8 ft walls, 2 coats.
Shopping list
- standard interior latex paint2.2 gal
- Primer1.1 gal
- Roller covers, tray, brush, tape, drop clothBasic kit
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Shared links include the current inputs and unit setting. Saved estimates stay local unless you enable Google Drive sync.
Assumptions in this estimate
- 350 sq ft per 1.0 gal coverage
- 10% waste buffer
- 21 sq ft per door and 15 sq ft per window deducted
- U.S. near average; pricing data: U.S. near average pricing
No saved estimates yet.
What this calculator estimates
This paint calculator starts from the measurements and options you enter, then estimates material quantity, waste, cost ranges, labor ranges, and a starter shopping list.
Results adapt to the selected region and unit settings, so the estimate is not locked to one market or measurement system.
Report confusing results, missing options, or assumptions that look off.
How this is calculated
- Quick room wall area is calculated as 2 x (length + width) x wall height.
- Detailed room mode can add ceiling area, trim area, and door-face paint as separate surfaces.
- Known wall area mode starts from the net paintable square footage you enter.
- Doors and windows are deducted with standard average areas in room modes.
- Gallons include coats and a 10% waste buffer, then round up to the nearest tenth.
Assumption register
| Item | Low | Typical | High | Source |
|---|---|---|---|---|
| Paint coverage | 300 | 350 | 400 | Sherwin-Williams paint calculator Checked 2026-06-21 · medium confidence |
| Waste buffer | 5 | 10 | 15 | Sherwin-Williams paint calculator Checked 2026-06-21 · medium confidence |
| Standard paint price | 34 | 45 | 55 | Homewyse paint benchmark and retail cross-checks Checked 2026-06-21 · low confidence |
Last reviewed: May 9, 2026. These values are planning defaults, not live prices.
Common mistakes
- Forgetting primer when covering stains, bare drywall, or a strong color change.
- Using one-coat math for a two-coat job.
- Ignoring textured or porous walls, ceilings, trim, or door faces.
FAQ
Should you buy exactly the calculated gallons?
Use the estimate as a planning number, then round to practical container sizes before buying.
When should you use detailed room mode?
Use detailed room mode when the ceiling, baseboards, casing, or door faces are part of the painting scope.
When should you use known wall area?
Use known wall area when you already measured net paintable square footage from drawings, a quote, or another tool.
Why show a range?
Paint brand, finish, wall condition, and region all change the final cost.
Can this paint calculator estimate cost by region?
Yes. The calculator uses the selected region and unit settings to adapt quantities, cost ranges, labor ranges, and assumptions.
How should you use the result before buying materials?
Use the result as a planning estimate, then compare it with a current supplier cart, contractor quote, or local project conditions before committing.
Limitations
This calculator estimates interior paint quantities from simplified room or area inputs. It does not include repairs, specialty primers, sprayed finishes, cabinet painting, or exterior work.
This estimate is for planning only. It is not a contractor quote, engineering advice, or permit review.
Next step
Measure once more, compare the result with a real quote or shopping cart, and review the assumptions before buying materials.
Read the how much paint do I need guide
Read the how much primer do I need guide
Read the one coat vs two coats of paint guide
Drywall calculator 
Flooring calculator