Paint Calculator
Calculate how many gallons of paint you need.
Last updated: June 13, 2026
Calculator
Results
2 coat(s) at 350 sq ft per gallon
Based on $35-$55 per gallon
How to Use This Calculator
- 1Enter room length, width, and ceiling height.
- 2Enter the number of doors and windows.
- 3Select the number of coats.
- 4View gallons needed and estimated cost.
Formula Explanation
Paint coverage is calculated by finding the net wall area (minus openings), multiplying by coats, and dividing by the paint coverage rate of 350 sq ft per gallon.
Variables:
Worked Examples
12×12 room, 8ft ceiling, 1 door, 2 windows, 2 coats
- 1. Net area = 384 − 21 − 30 = 333 sq ft
- 2. Total area = 333 × 2 = 666 sq ft
- 3. Gallons = 666 / 350 = 1.9 → 2 gallons
Why Use This Calculator
- Buy the right amount of paint — no waste, no extra trips.
- Accounts for doors, windows, and multiple coats.
- Provides cost estimates to help with budgeting.
- Works for any rectangular room.
Tips & Best Practices
- Two coats give the best coverage and color depth — one coat rarely looks professional.
- Dark colors over light may need 3 coats for full coverage.
- Buy all paint at once from the same batch to ensure consistent color.
- One gallon of primer should also be budgeted if painting over dark colors or new drywall.
Common Mistakes to Avoid
❌ Buying paint for only one coat to save money.
✅ Two coats are almost always necessary. One coat looks uneven and wears faster.
❌ Not accounting for primer, which is separate from paint.
✅ Budget one gallon of primer per 2 gallons of paint when covering new or dark surfaces.
❌ Using 400 sq ft/gallon (manufacturer claim) instead of realistic 350 sq ft.
✅ 350 sq ft/gallon is more realistic for textured walls and roller application.
Frequently Asked Questions
How much does one gallon of paint cover?
How many coats of paint do I need?
Should I paint walls or trim first?
How long does paint take to dry?
Is expensive paint worth the extra cost?
Embed This Calculator
Add the Paint Calculator to your website for free. Copy the code below and paste it into your HTML.
<iframe src="https://redicalc.com/embed/construction/paint-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="Paint Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.
By using this site, you agree to our Terms of Use and Privacy Policy. © 2026 RediCalc.com. All rights reserved.