Paint Calculator
Paint Coverage Quick Reference
Gallons needed for 2 coats at 350 sq ft/gallon coverage.
| Room Size | Wall Area (sq ft) | After Openings | Gallons (2 coats) | With Ceiling |
|---|---|---|---|---|
| 10 x 10, 8' walls | 320 | 284 | 2 | 3 |
| 10 x 12, 8' walls | 352 | 316 | 2 | 3 |
| 12 x 12, 8' walls | 384 | 348 | 2 | 3 |
| 12 x 16, 8' walls | 448 | 412 | 3 | 4 |
| 14 x 16, 8' walls | 480 | 444 | 3 | 4 |
| 16 x 20, 8' walls | 576 | 540 | 4 | 5 |
| 20 x 20, 8' walls | 640 | 604 | 4 | 6 |
How We Calculate This
This paint calculator uses established formulas and industry-standard data to provide accurate estimates.
- Enter your specific values into the calculator fields above
- Our algorithm applies the relevant formulas using your inputs
- Results are calculated instantly in your browser — nothing is sent to a server
- Review the detailed breakdown to understand how each factor affects your result
These calculations are estimates based on standard formulas. For critical decisions, always consult a qualified professional.
How to Convert Oven Recipes to Air Fryer
Calculating paint quantity starts with finding your total paintable wall area, subtracting openings, then dividing by the paint's coverage rate per gallon.
The basic rule:
- Wall area = perimeter (2 × length + 2 × width) × height, minus doors (21 sq ft each) and windows (15 sq ft each)
- One gallon of interior paint covers 350-400 sq ft on smooth walls; textured walls may drop to 250-300 sq ft
- Always plan for 2 coats — the first coat seals the surface and the second provides full, even coverage
This calculator rounds up to the nearest gallon. If you are close to a whole number, consider buying quarts to supplement. Most paint stores will tint quarts to match your gallon color. Keep leftover paint for future touch-ups.
When Would You Use This Calculator?
This paint calculator is designed for anyone who needs quick, reliable estimates without complex spreadsheets or professional consultations.
- When you need a quick estimate before committing to a purchase or project
- When comparing different options or scenarios side by side
- When planning a budget and need to understand potential costs
- When you want to verify a quote or estimate you've received from a professional
- When teaching or learning about the concepts behind these calculations
Frequently Asked Questions
How many square feet does a gallon of paint cover?
A gallon of interior paint covers 350-400 square feet on smooth, primed walls. Textured or porous surfaces reduce coverage to 250-300 square feet. Exterior paint typically covers 250-350 square feet per gallon depending on the surface texture.
Do I really need 2 coats of paint?
Yes, two coats are recommended for most projects. The first coat seals the surface and provides a base, while the second coat ensures uniform color and full coverage. You might get away with one coat if you are painting the exact same color over a well-prepared surface.
How much paint do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings has about 384 square feet of wall area. After subtracting a door and two windows, that is roughly 333 square feet. At 350 sq ft/gallon with 2 coats, you need about 2 gallons for the walls, plus 1 gallon for the ceiling if painting it.
Should I buy paint in gallons or 5-gallon buckets?
If you need 3 or more gallons of the same color, a 5-gallon bucket is usually cheaper per gallon and ensures color consistency. For smaller jobs, individual gallons are fine. Always buy all your paint at once — even the same color code can vary slightly between batches.
How do I estimate paint for trim and baseboards?
Trim paint (doors, baseboards, crown molding) typically requires 1 quart per standard door (both sides plus frame) and about 1 quart per 100-150 linear feet of trim. A typical room with one door and standard baseboards needs about 1-2 quarts of trim paint.
What is the difference between flat, eggshell, and satin paint?
Flat/matte paint hides imperfections but is hard to clean — best for ceilings and low-traffic areas. Eggshell has a slight sheen and is washable — ideal for living rooms and bedrooms. Satin is more durable and moisture-resistant — best for kitchens, bathrooms, and trim.