Paint Calculator for Any Room
This paint calculator works out exactly how much paint you need before you head to the store. Enter your room dimensions, subtract doors and windows, pick a paint type and number of coats, and get an accurate quantity in liters or gallons in seconds.
It goes well beyond a plain area sum. Interior and exterior modes, surface texture, a waste buffer, multi-room totals, and a built-in cost estimator all factor in, so you can plan a whole repaint and budget the purchase with confidence — whether you are a homeowner doing one bedroom, a contractor quoting a job, or a designer pricing a renovation.
How to Use the Paint Calculator
Choose Interior or Exterior
Pick Interior or Exterior. Exterior paint covers less area on rougher, weather-exposed surfaces, so the calculator lowers the coverage rates and hides the ceiling option in exterior mode.
Enter room dimensions
Type the Length, Width, and Height. Wall area is computed automatically. In interior mode you can switch on Include ceiling to paint it as well.
Add doors and windows
Openings do not need paint, so subtract them. Click a preset size for a common door or window, or add a custom opening with your own measurements, then set the quantity for repeated openings.
Configure the paint
Choose a Paint type (Latex, Oil-based, Primer, or Custom), set the Number of coats (1, 2, or 3), pick a Surface type (Smooth or Textured), and keep the 10% waste toggle on for a realistic buffer.
Review the results
See the total paint needed, an area breakdown (wall, ceiling, openings, and paintable area), a 3D room diagram, and a suggested number of cans to buy for each common size.
Add more rooms and estimate cost
Use the + button to add rooms — each keeps its own settings — and the ... menu to rename, duplicate, or delete them. Open the Cost Estimator, enter a price per can, then click Export PDF to download a summary for the store.
Features
Interior and Exterior Modes
Switch between interior and exterior painting, each with its own coverage rates. Ceiling painting is available in interior mode and disabled for exterior.
Accurate Wall Area
Uses the standard formula 2 × (length + width) × height and subtracts every opening to give the exact paintable surface area.
Door & Window Presets
One-click presets for common doors (0.9×2.1, 0.8×2.0) and windows (1.2×1.2, 1.5×1.2, 0.6×0.6), plus custom openings with adjustable quantities.
Paint Type Coverage
Latex, Oil-based, and Primer each use realistic coverage rates per mode, or enter a Custom rate straight from your paint can label.
Surface Texture & Coats
Choose 1, 2, or 3 coats, and select Textured to add about 20% more paint for rough surfaces like stucco or knockdown.
10% Waste Factor
An optional 10% buffer accounts for roller and brush absorption, spills, and cutting in, so you do not run short mid-project.
3D Room Diagram
An isometric view shows your walls, ceiling, and openings, updating in real time as you change the dimensions.
Multi-Room Support
Add as many rooms as you need, rename, duplicate, or delete each one, and see a summary with per-room amounts and a grand total.
Metric & Imperial Units
Switch between meters/liters and feet/gallons with one click — all dimensions, coverage rates, and stored rooms convert automatically.
Can Size Suggestions
From the total paint needed, see how many cans to buy at 1L, 5L, and 18L (metric) or 1 qt, 1 gal, and 5 gal (imperial).
Cost Estimator
Enter the price per can and pick a can size to see the total cost. The currency picker covers many currencies and detects your locale.
Export PDF & Auto-Save
Download a clean PDF with rooms, areas, quantities, can suggestions, and cost. Your work auto-saves and restores on your next visit.
Frequently Asked Questions
How much paint do I need for a room?
Enter the room's length, width, and height to get the wall area, then subtract doors and windows. The calculator multiplies the paintable area by your number of coats and divides by the paint's coverage rate (with an optional 10% waste buffer) to give the total in liters or gallons.
How many square feet does a gallon of paint cover?
It depends on the paint type and surface. The calculator uses realistic per-mode rates — for example, interior latex covers roughly 10–12 m²/L (about 400–490 ft²/gal), while exterior latex covers less because outdoor surfaces are rougher. Switch to imperial units to see every rate and result in square feet and gallons, or enter a Custom rate from your can label.
How do I account for two coats?
Set the Number of coats to 2 and the total paint scales accordingly. Most projects need 2 coats for even coverage; use 1 for touch-ups over the same color, or 3 when covering a dark color with a lighter one.
Should I subtract windows and doors?
Yes. Openings are not painted, so add each door and window — using a preset size or a custom one — and the calculator removes their area from the total. Adjust the quantity if you have several of the same size.
How much primer do I need?
Select Primer as the paint type. It has its own coverage rate (around 8–10 m²/L interior, 6–8 m²/L exterior), so the result reflects a base coat on new drywall or before a dramatic color change. To plan primer and topcoat separately, calculate them as two passes or two rooms.
Does a rough or porous surface use more paint?
Yes. Textured surfaces such as stucco, knockdown, or popcorn have more area in their grooves and absorb more paint. Selecting Textured reduces the effective coverage by 20%, so your estimate includes the extra paint needed to fill the surface.
What is the 10% waste factor?
Some paint is always lost to roller and brush absorption, spills, and cutting in around edges. The 10% waste toggle adds a realistic buffer so you do not come up short. You can turn it off for the exact calculated amount, but keeping it on is generally recommended.
Can I calculate paint for multiple rooms at once?
Yes. Click the + button to add rooms, and use the ... menu to rename, duplicate, or delete each one. A summary shows the paint needed per room plus the total across all rooms, so you can plan a single purchase for the whole project.
How accurate is this calculator?
It gives a reliable estimate from standard coverage rates with an optional 10% buffer. Actual usage can vary with application method (roller vs. spray), paint brand, wall condition, and technique, so treat the result as a confident planning figure.
Is my data saved, and can I export it?
Your rooms, dimensions, mode, units, and settings are saved automatically in your browser and restored on your next visit — no account needed. Click Export PDF to download a formatted summary with all room details, paint quantities, can suggestions, and cost estimates to take to the store.
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