Wall Paint Calculator
Planning to paint a room or your entire home? One of the most common issues DIY painters and even professionals face is figuring out exactly how much paint to buy. Buy too much, and you waste money. Buy too little, and you risk running out halfway through the job. That’s where our Wall Paint Calculator comes in.
This simple, yet powerful online tool helps you determine how much paint is needed for any given project—whether you’re touching up one wall or repainting a full room. It factors in wall dimensions, the number of coats, paint coverage per liter, and even subtracts space taken up by doors and windows.
🛠 How to Use the Wall Paint Calculator: Step-by-Step Guide
Using this tool is straightforward and only takes a few moments. Here’s how:
- Enter Wall Height (in meters)
Measure the height from floor to ceiling for the wall(s) you want to paint. - Enter Wall Width (in meters)
This is the horizontal length of the wall. If you’re painting multiple walls of the same size, just enter one measurement and adjust the wall count later. - Number of Walls
Input how many walls of this size you’re painting. - Number of Doors and Windows
Since paint isn’t needed where doors and windows are, you can input how many of each are on the wall(s). - Select Average Door and Window Size
Choose from standard, small, or large options. These presets are based on average sizes to subtract surface area accurately. - Paint Coverage Per Liter
Choose the paint’s coverage efficiency (typically provided on the paint can). Most paints cover 8–12 sq. meters per liter. - Number of Coats
Standard jobs require 2 coats. Choose 1 for touch-ups or 3 for bold color changes or rough surfaces. - Click “Calculate”
The calculator will show:- Total wall area
- Total area of doors & windows
- Paintable area
- Liters of paint required
- A buying recommendation (e.g., how many 5L or 2.5L cans)
🎯 Practical Example: Painting a Bedroom
Let’s say you want to repaint a bedroom with the following details:
- Wall Height: 2.5 meters
- Wall Width: 4 meters
- Number of Walls: 4
- Doors: 1 standard door
- Windows: 2 standard windows
- Paint Coverage: 10 sq. meters per liter
- Coats Required: 2
Results:
- Total Wall Area = 2.5 × 4 × 4 = 40 sq. meters
- Doors & Windows Area = (1 × 1.89) + (2 × 1.44) = 4.77 sq. meters
- Paintable Area = 40 – 4.77 = 35.23 sq. meters
- Paint Needed = (35.23 × 2) / 10 = 7.05 liters
- Recommendation = Buy 1 × 5L can and 1 × 2.5L can
This quick estimate saves you a trip back to the store and ensures you’re well-prepared.
🧠 Additional Tips & Use Cases
- Different Rooms, Different Needs: Kitchens and bathrooms often have tiles, reducing paintable area. Always measure only the paintable surface.
- Ceiling Painting: To include ceilings, just treat them as additional “walls” using height and width.
- Surface Type Matters: Rough surfaces like bare drywall or stucco may need more paint—choose the 8 sq. m/liter option for safety.
- Multiple Colors? Run the calculator once for each color zone or accent wall.
❓ Frequently Asked Questions (FAQs)
1. What’s the average coverage of paint per liter?
Most standard wall paints cover around 10 square meters per liter. Premium options may cover 12+, and textured paints might cover less.
2. How do I calculate for ceilings?
Treat the ceiling as a flat wall. Use its length and width as inputs for height and width in the calculator.
3. Do I need to subtract doors and windows?
Yes, the calculator does it for you. Enter their counts and average sizes to get an accurate paintable area.
4. Why are coats important in the calculation?
Each coat requires a full layer of paint. Two coats double your paint requirement. Always include the correct number for your project.
5. What if I have different wall sizes?
Run the calculator separately for each set of different-sized walls, then add the results together.
6. Can I use this for exterior walls?
Yes, just make sure to account for material differences and harsher exposure. Use lower paint coverage rates (like 8 sq. m/liter).
7. What if I’m using primer first?
Calculate separately for primer and paint. Many primers also list their coverage per liter.
8. Can I round down the paint needed?
It’s safer to round up. Always buy slightly more than needed to account for touch-ups and absorption.
9. Does wall texture affect paint needed?
Yes, rough or unprimed surfaces absorb more paint. Choose a lower coverage value in the dropdown.
10. How many coats should I apply?
For color changes or full repaints, 2–3 coats are standard. Touch-ups may only need 1.
11. Is leftover paint useful?
Absolutely. Keep extra for future touch-ups or repairs.
12. Can I reuse this for furniture or small items?
Yes, though you’ll need to input accurate surface area measurements manually.
13. What are standard door and window sizes?
Doors: ~0.9 × 2.1 meters
Windows: ~1.2 × 1.2 meters
The tool uses these for quick subtraction.
14. Should I factor in trim and moldings?
Yes, but this tool focuses on main surfaces. Add a small margin or calculate trim separately.
15. Is this tool accurate for vaulted or angled ceilings?
Not directly. You’ll need to break the surface into smaller rectangles or triangles and input them individually.
16. Does the time of year affect painting?
Yes. Paint adheres best in moderate humidity and temperatures. Avoid extreme cold or heat.
17. Can I save my results?
Copy the output or take a screenshot. For full functionality, consider exporting data (feature coming soon!).
18. What’s the best way to measure walls?
Use a measuring tape and record in meters. For large areas, use a laser distance measurer.
19. Do I need to clean the wall before painting?
Yes. Dust, grease, and moisture affect paint bonding. Always prep the surface.
20. Can I trust the buying recommendations?
Yes, they’re based on calculated volume and available can sizes. Still, verify local store offerings.
✅ Final Thoughts
Whether you’re repainting a single room or your entire house, our Wall Paint Calculator ensures you’re buying just the right amount of paint—no more, no less. Save time, money, and hassle by planning properly.
Use this free tool any time you’re planning a painting project and take the guesswork out of home improvement.
Ready to get started? Scroll back up and calculate your paint needs now!