How many square feet does 1 gallon cover?
Most interior paints cover about 300-400 square feet per gallon per coat, with 350 square feet as a common planning baseline.
How Much Paint Do I Need? (Walls, Ceilings & Trim Guide 2026)
Quick Answer
How much paint do you need? One gallon of paint covers 350–400 sq ft per coat on smooth surfaces. A standard 12×12 room with 8-ft ceilings typically needs 2–3 gallons for walls with two coats.
Quick calculation: Wall area = 2(L + W) × H. Multiply by coats. Divide by 350. Round up.
Room estimate examples:
- 10×10 room: ~2 gallons (two coats)
- 12×12 room: ~3 gallons (two coats)
- 15×20 room: ~4–5 gallons (two coats)
Mini Paint Calculator
Estimated gallons
Estimated gallons: 2.00
Assumes ~350 sq ft/gal/coat. Textured walls and dark colors may require more.
Paint Needed by Room Size (Examples)
| Example | Paintable Area Basis | Estimated Gallons (2 coats) |
|---|---|---|
| 10x10 room @ 8 ft ceilings | ~320 sq ft walls | ~2 gallons |
| 12x12 room @ 8 ft ceilings | ~384 sq ft walls | ~3 gallons |
| 12x20 room @ 9 ft ceilings | ~576 sq ft walls | ~4 gallons |
| 2,000 sq ft home interior walls | Whole-home ballpark | ~15-25 gallons |
Assumptions: around 350 sq ft coverage per gallon per coat, two coats, no door/window deductions, and standard smooth-to-lightly textured walls. Heavy texture and deep color changes can increase total gallons.
Rough Whole-House Interior Paint Estimate (Quick Guide)
These are rough planning ranges for walls + ceilings with two coats (standard 8–9 ft ceilings). Actual needs vary by layout, windows/doors, texture, and color changes.
- 1,500 sq ft home: ~12–18 gallons
- 2,000 sq ft home: ~15–25 gallons
- 2,500 sq ft home: ~20–30 gallons
- 3,000 sq ft home: ~25–35 gallons
This is only a ballpark. For accurate results, estimate room-by-room using the Paint Calculator.
The Simple Formula (How to Calculate Paint)
Start with wall area: 2(L+W)H. Multiply that result by the number of coats, then divide by 350 sq ft per gallon as a baseline coverage rate. Round up to the next full gallon so you are not short mid-job.
If you need a quick coverage check for non-standard products, use the Paint Coverage Calculator.
Paint Coverage Rates by Surface Type (Per Gallon)
| Surface type | Typical coverage (sq ft / gallon) | Coats usually needed | Notes |
|---|---|---|---|
| Interior walls (smooth) | 350–400 | 2 | Standard interior coverage |
| Interior walls (textured) | 300–350 | 2 | Texture absorbs more paint |
| Exterior siding/stucco | 250–350 | 2 | Porosity varies widely |
| New drywall (primer) | 200–250 | 1 | Primer covers less than paint |
| Ceilings (smooth) | 350–400 | 1–2 | Flat paint; fewer coats sometimes |
| Ceilings (textured/popcorn) | 250–300 | 2 | Heavy texture absorbs a lot |
| Trim/doors (smooth) | 400–450 | 2 | Smooth surfaces; thin coats |
| Dark → light color change | 300–350 | 3 | Or tinted primer + 2 coats |
Coverage varies by paint quality, surface porosity, and application method. When in doubt, round up to avoid running out mid-project.
Ceilings: How Much Paint Do You Need?
Ceiling area is usually length x width. For smooth ceilings, one to two coats is common depending on color change and stain coverage. Popcorn or heavily textured surfaces often need more paint, often 10-20% extra because of increased surface area and roller absorption.
Trim & Doors: Paint Needed
For trim, estimate by linear feet, then convert to paintable area using average trim width. That gives a cleaner estimate than guessing by floor square footage. For doors, a common rule is roughly 0.5-1 quart per coat per standard door depending on panel detail and finish quality.
Primer vs Paint
Primer and paint do different jobs. Primer improves adhesion and seals porous surfaces, while paint provides color and a durable finish. Primer typically covers 200–250 sq ft per gallon, which is less than standard wall paint.
Use primer when:
- Painting new, unpainted drywall or repaired patches
- Covering stains (water, smoke) or tannin bleed from wood
- Switching from very dark colors to light colors
- Painting over glossy surfaces where adhesion is a concern
- Working with raw wood or highly porous surfaces
For exact primer quantities based on your measurements, use the Primer Calculator.
Common Mistakes (Avoid Overbuying)
- Not measuring walls and ceilings before buying paint.
- Not accounting for heavy texture or porous surfaces.
- Choosing the wrong sheen for the room and repainting sooner.
- Not rounding up gallons for full-coat consistency.
- Forgetting primer on new drywall or stain-prone surfaces.
- Not keeping enough paint for touch-ups and repairs.
FAQ
How much paint for a 12x12 room?
For 12x12 walls at 8 ft height and two coats, many jobs land near 3 gallons after rounding up, before major deductions.
Do I need 2 coats?
In most repaints, two coats give more uniform color and durability, especially when changing colors or using lower-sheen finishes.
How much extra should I buy for touch-ups?
Plan to keep around 5-10% extra paint or at least a quart per color for future touch-ups and patch repairs.
How much paint for ceilings?
Ceiling paint is based on floor area (length x width), then adjusted for coats and texture. Textured ceilings can need extra material.
Paint vs primer: what's the difference?
Primer seals and improves adhesion, while paint provides final color and finish. New drywall and stain-prone surfaces often need primer first.