Result
3 gallons to buy
After subtracting openings and adding 10% waste, plan for 2.3 gallons.
- Paintable area
- 360 sq ft
- Adjusted coverage area
- 792 sq ft
- Calculated gallons
- 2.3 gal
More
Optional equipment checkWhat to compare before buying
Compare paint supplies by roller nap, tray size, brush quality, tape, drop cloths, primer needs, and the coverage printed on the paint label.
Buying checklist
At a glance
- Cost
- Free
- Login
- Not required
- Best use
- Estimate how many gallons of paint to buy based on wall area, doors and windows, number of coats, coverage per gallon, and waste.
- Output
- Browser result with print and PDF options
- Reviewed
- 2026-07-09
Result summary
Quick answer
With the sample inputs, this calculator returns 3 gallons to buy. Paintable area: 360 sq ft. Use 3 gallons to buy as a buying estimate, then confirm label coverage, coat count, primer needs, surface condition, and a small touch-up buffer.
Publisher Published by EverydayCalc Editorial Editorial standards and limitations
Each calculator shows its formula and defines the inputs. Worked examples make the math checkable. The page also names the limits that can change the result.
Last calculation review:
Review scope: formula implementation, example parity, visible assumptions, source links, and result presentation. This is editorial and calculation QA, not professional financial, tax, legal, medical, engineering, or safety review.
Results are estimates based on the inputs provided and the assumptions shown on this page. For financial, tax, legal, medical, or other high-stakes decisions, verify results with a qualified professional or official source.
Instructions
How to use this calculator
Open the short walkthrough for choosing and checking inputs.
Add the area of each wall, subtract major openings, and enter the number of coats. Fresh drywall and dramatic color changes may need extra paint.
Page guide
On this page
Jump directly to the part of the calculator you need.
Calculation details
Formula and methodology
See the exact math used to produce the result.
Paint needed = paintable area multiplied by coats, divided by coverage per gallon, plus waste.
Before acting
Assumptions to check
Review the real-world details that can change the estimate.
The key inputs are Total wall area, Doors and windows, Number of coats, Coverage per gallon, Waste allowance. Confirm wall area, coats, primer, texture, waste, touch-ups, windows, doors, and product coverage before buying paint.
More guidance Examples, methodology, and planning checks Open the worked example, review notes, reference tables, and practical next checks.
Why waste allowance helps
A small waste factor covers roller loading, touch-ups, rough surfaces, and measurement error.
When to use this calculator
- Estimating materials before shopping
- Checking project coverage and waste
- Building a simple supply list
Tips for better estimates
- Measure paintable wall area and keep doors, windows, coats, primer, and color change separate.
- Round up to full gallons if the wall is textured, patched, or changing color strongly.
- Save extra paint for touch-ups before disposing of cans.
How this calculator is reviewed
This page is checked for inputs, formulas, examples, assumptions, topic fit, and related links. For this calculator, the review also covers wall area, coats, primer, texture, waste, touch-ups, windows, doors, and product coverage.
The sample result is covered by automated tests, and the page links to related calculators and, where available, supporting guides so readers can check the assumptions before acting. If a formula, label, or assumption looks off, send the page URL and your inputs through the contact page.
How this estimate was built
This page subtracts openings from wall area, multiplies by coats, applies product coverage per gallon, adds waste, and rounds to practical paint quantities.
Worked example
Example inputs: Total wall area: 400 sq ft; Doors and windows: 40 sq ft; Number of coats: 2; Coverage per gallon: 350 sq ft; Waste allowance: 10 %. With those values, the calculator returns 3 gallons to buy. After subtracting openings and adding 10% waste, plan for 2.3 gallons.
Paint gallons by room size
| 10x10 room, 2 coats | Usually 1 to 2 gallons |
|---|---|
| 12x12 room, 2 coats | Usually about 2 gallons |
| Large living room | Usually 2 to 3 gallons |
| Ceiling or dark color change | Add paint or primer before buying |
Example scenarios
- A bedroom repaint can use 3 gallons to buy as the gallons target for walls, then add a touch-up allowance if the color change is strong.
- For patched drywall, add primer before paint so coverage does not fall short.
- For textured walls or deep colors, use the estimate as a minimum and round up before buying.
Quick reference chart
| Sample result | 3 gallons to buy |
|---|---|
| Paintable area | 360 sq ft |
| Adjusted coverage area | 792 sq ft |
| Calculated gallons | 2.3 gal |
| Best next step | Buy the calculated gallons for one color and add extra paint for touch-ups if the wall is rough, patched, or changing color dramatically. |
FAQs
Paint Coverage Calculator questions
Can I use this as my final paint order?
Use it as a planning estimate, then confirm wall area, windows and doors, coats, primer, texture, touch-ups, product coverage, sheen, and color change.
Should I add extra paint?
Usually yes. Extra paint helps with textured walls, patches, roller loss, deep color changes, uneven coverage, and future touch-ups.
What should I check before buying?
Check the paint label coverage, primer needs, wall repairs, surface texture, number of coats, and whether ceilings or trim are included.
Should I subtract trim?
Most quick estimates only subtract large doors and windows. Trim usually does not change the gallon count much.
What coverage number should I use?
Many paints cover roughly 300 to 400 square feet per gallon, but check the can for the exact product.
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Common planning mistakes
Forgetting primer, ignoring color changes, subtracting too many small openings, and not saving paint for touch-ups.
Cite or embed this calculator
If this calculator helps a blog post, classroom resource, forum answer, seasonal guide, or local planning page, link to the canonical calculator URL so readers can run their own numbers and check the assumptions.
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