Paint Calculator
Calculate how much paint you need for a room.
Wall area
45.00 m²
Paint needed (L)
9.00 L
Paint needed (gal)
2.38 gal
How to use Paint Calculator
Enter Room Dimensions
Input your room's length, width, and height in feet or meters using the input fields labeled 'Length', 'Width', and 'Height'. The calculator accepts decimal values for precise measurements.
Select Paint Coverage Rate
Choose your paint type from the dropdown menu or enter the coverage rate in square feet per gallon. Standard latex paint covers 350-400 sq ft/gallon; premium paint covers 250-350 sq ft/gallon. The default value is 350 sq ft/gallon.
Specify Number of Coats
Use the 'Number of Coats' selector to choose 1, 2, or 3 coats. Most rooms require 2 coats for even coverage. Select the appropriate number using the radio buttons or dropdown.
Adjust for Windows and Doors
Toggle the 'Include Windows/Doors' checkbox and enter the number of windows and doors. Each window equals approximately 10 sq ft and each door equals 20 sq ft. The calculator automatically deducts these areas.
View Your Paint Estimate
Click the 'Calculate' button to instantly see results displayed in the 'Results' panel. View total square footage, gallons needed, and cost estimate if you entered your paint price per gallon.
How to Calculate Paint for a Room — Free Online Calculator Guide
Calculating how much paint you need for a room is simpler than you think. Using a free online paint calculator takes the guesswork out of your painting project and saves you money by eliminating over-purchasing.
How Much Paint Do You Need?
The amount of paint required depends on four key factors: room dimensions, paint coverage rate, number of coats, and surface deductions for windows and doors. A single gallon of standard latex paint typically covers 350-400 square feet per coat. Most rooms require two coats for professional-looking results.
Step-by-Step Guide to Using Paint Calculator
Step 1: Measure Your Room Accurately Measure the length, width, and height of your room in feet. Write these down before opening the calculator. For example, a room measuring 12 feet long, 10 feet wide, and 8 feet high would be entered as those exact numbers.
Step 2: Calculate Total Wall Area The Paint Calculator automatically computes this, but to understand: multiply room height by the perimeter (2 × length + 2 × width). For our example: 8 feet × (2 × 12 + 2 × 10) = 8 × 44 = 352 square feet.
Step 3: Account for Windows and Doors Windows and doors don't need painting. A standard window is approximately 10 square feet; a standard door is 20 square feet. If your room has 2 windows and 1 door, that's 40 square feet to subtract. The calculator handles this automatically when you input these numbers.
Step 4: Choose Your Paint Type Different paints have different coverage rates. Select your paint type or enter the coverage rate from your paint can. Premium paints may only cover 250-350 sq ft/gallon, while budget paints often cover up to 400 sq ft/gallon.
Step 5: Select Number of Coats Most painting projects require 2 coats for even coverage. Use 1 coat for touch-ups. Choose 3 coats if you're painting a light color over dark walls or using an unusual color that needs extra coverage.
Step 6: Get Your Result Click 'Calculate' to see how many gallons you need. The calculator displays results for one coat and total coats. For example: "You need 2.5 gallons for 1 coat, 5 gallons for 2 coats."
Tips for Accurate Paint Calculations
Consider Wall Texture Textured walls absorb more paint than smooth surfaces. If your walls have texture, increase your paint estimate by 10-15%. Popcorn ceilings require 20-25% additional paint. Reduce the coverage rate in the calculator to account for this extra absorption.
Account for Color Coverage Dark colors over light surfaces need extra coats. Painting white walls with dark paint might require 3 coats. Conversely, painting dark walls with white paint also typically needs 3 coats. Light colors over similar light colors may only need 1 coat.
Add 10% Buffer Painting always involves some waste from brushes, roller absorption, and touch-ups. Add 10% to your calculated amount to ensure you don't run short mid-project.
Check Paint Can Coverage Manufacturers list coverage rates on paint cans. These are estimates based on smooth surfaces. Actual coverage varies by surface type, humidity, and application technique.
Common Paint Calculation Mistakes to Avoid
Mistake 1: Forgetting to subtract window and door areas. This leads to over-purchasing paint, wasting money.
Mistake 2: Using only one coat for full coverage. Most projects genuinely need two coats, especially with color changes.
Mistake 3: Ignoring surface texture. Textured walls consume significantly more paint than smooth surfaces.
Mistake 4: Calculating only wall paint without ceiling. If painting the ceiling, add its square footage (length × width) separately or use the calculator twice.
Frequently Asked Paint Quantity Questions
How many gallons of paint does one gallon actually cover? One gallon covers approximately 350-400 square feet for one coat on smooth, primed walls. Coverage decreases with texture, primer, or two coats.
What's the difference between gallons and quarts? 1 gallon = 4 quarts. Buy quarts for small touch-ups or test areas. Buy gallons for full rooms.
How much does a gallon of paint cost? Quality interior latex paint ranges from $20-60 per gallon. Budget paint is cheaper but requires more coats; premium paint costs more but covers better.
Ready to Paint? Start Calculating
Using the free Paint Calculator above, enter your room measurements and get an instant, accurate estimate of paint needed. This prevents over-purchasing, reduces waste, and ensures your painting project stays within budget. No registration required — calculate as many rooms as you need, completely free.
Measure your space, input the dimensions, and let the calculator do the math. You'll have your paint shopping list ready in seconds.