Paint Calculator Estimate how much paint you need — for walls, ceilings, trim, and exteriors — with realistic coverage an...
Paint Calculator
Estimate how much paint you need — for walls, ceilings, trim, and exteriors — with realistic coverage and prep guidance.
✅ Wall area = Perimeter × Height − Doors/Windows**
Example: 12×12 room, 8 ft height: • Perimeter = (12 + 12) × 2 = 48 ft • Wall area = 48 × 8 = **384 sq ft** • Minus 1 door (21 sq ft) + 2 windows (30 sq ft) = **333 sq ft paintable area**
⚠️ Don’t measure floor area** — a 12×12 room has 144 sq ft floor but ~350 sq ft walls!
📏 Tips**:
- Measure height to ceiling (not standard 8 ft — many are 8'6" or 9')
- Standard door = 21 sq ft, window = 15 sq ft
- Add 10% for cut-in, texture, and waste
✅ Always prime** if:
- New drywall or plaster
- Stains (water, smoke, ink)
- Going from dark to light (e.g., navy → white)
- Switching sheens (gloss → flat)
⚠️ Skipping primer risks**:
- Color bleed-through
- Poor adhesion → peeling
- More topcoats needed → higher cost
💡 Pro Tip**:
- For new drywall: use PVA or drywall primer ($20/gal)
- For stains: use shellac-based (BIN) or oil-based (Kilz Original)
- Never use paint + primer in one — it’s marketing hype!
| Sheen | Best For | Pros | Cons |
|---|---|---|---|
| Flat/Matte | Ceilings, low-traffic walls | Hides imperfections | Not washable |
| Eggshell | Living rooms, bedrooms | Soft glow, wipeable | Moderate durability |
| Satin | Kitchens, bathrooms, hallways | Washable, durable | Shows flaws |
| Semi-Gloss | Trim, doors, cabinets | High durability, moisture-resistant | High shine, highlights texture |
📉 2025 Price Benchmarks** (per gallon):
- Budget (Glidden, Valspar): $25–$35
- Mid-Tier (Behr, Sherwin-Williams ProMar): $40–$55
- Premium (Benjamin Moore Regal, Sherwin-Williams Emerald): $65–$85
➡️ Room Mode
Enter length, width, height, doors, and windows. The tool deducts openings and calculates wall area.
➡️ Multi-Room Mode
Quick estimate for whole-house projects (uses avg. room sizes).
➡️ Exterior Mode
Enter total sq ft and trim — adjusts for siding type (brick = 30% less coverage).
You’ll get:
- Paintable wall area
- Gallons needed (incl. waste & primer)
- Paint cost (low/mid/high tier)
- Pro estimate (national avg. $3.50/sq ft)
Note: Ceiling = length × width (add 25% if textured). Trim = linear ft × 0.2 gal/100 ft.