Paint Calculator: Estimate How Much Paint You Need

Figure out exactly how much paint you'll need for your next home improvement project. Account for walls, ceilings, doors, and windows with ease.

Room Dimensions & Details

Room Length (ft):

Room Width (ft):

Room Height (ft):

Other Factors

Number of Coats:

Number of Doors:

Number of Windows:

Paint Coverage Rate (sq ft / gallon): Typically 300-400 sq ft (or 28-37 sq m) per gallon (or 3.785 L).

Paint Needed

Total Paint Needed:

0.0 Gallons

0.0 Liters

Estimated Area to Paint:

0.0 Sq Ft

0.0 Sq Meters

How to Use This Paint Calculator

Our paint calculator simplifies the process of estimating how much paint you'll need for your next project. Follow these simple steps:

Enter Room Dimensions: Input the length, width, and height of your room. You can choose between feet (imperial) or meters (metric) units.
Specify Number of Coats: The default is 2 coats, which is typical for most painting projects, especially when changing colors or covering imperfections.
Account for Doors and Windows: Enter the number of doors and windows in the room. The calculator automatically subtracts standard areas for these openings, providing a more accurate estimate.
Adjust Coverage Rate (Optional): The default paint coverage rate is 350 sq ft/gallon (approx. 32.5 sq m/gallon), a common average. However, if your paint label specifies a different rate, you can adjust this value for increased accuracy.
Click "Calculate Paint": The tool will instantly provide the total estimated paint needed in both gallons and liters, along with the total area to be painted.
Copy Results: Use the "Copy Result" button to quickly save your estimated paint quantity.

Assumptions & Formulas

This calculator uses industry-standard assumptions and formulas to provide reliable estimates:

Wall Area: Calculated as (2 * (Length + Width) * Height).
Ceiling Area: Calculated as Length * Width.
Standard Door Area: Each door is assumed to be 21 sq ft (1.95 sq m).
Standard Window Area: Each window is assumed to be 15 sq ft (1.4 sq m).
Total Paintable Area: (Wall Area + Ceiling Area - Area of Doors - Area of Windows) * Number of Coats.
Paint Needed (Gallons): Total Paintable Area / Coverage Rate per Gallon.
Conversion: 1 US Gallon ≈ 3.785 Liters.
Unit Conversions: 1 ft = 0.3048 m; 1 sq ft = 0.0929 sq m.

Disclaimer: These calculations are estimates. Actual paint required may vary based on surface porosity, paint thickness, application method, and specific paint product characteristics. Always purchase slightly more paint than estimated to ensure you have enough for touch-ups.

Common Questions (FAQ)

What if my doors or windows are not standard size? ▼

Our calculator uses standard approximations for door and window areas. If your openings are significantly larger or smaller, you can estimate their total area, and adjust the total wall area manually before using the calculator, or add/subtract from the final paint estimate. For example, if you have very large French doors, you might calculate their area and adjust the wall area accordingly.

Why do I need two coats of paint? ▼

Most painting projects benefit from two coats for a uniform, durable, and vibrant finish. A single coat may appear streaky, especially when covering a darker color or using lighter paint. The second coat ensures full coverage and color saturation.

What does "paint coverage rate" mean? ▼

The paint coverage rate indicates how much area a single unit (e.g., gallon or liter) of paint can cover. This value is usually found on the paint can label and can vary depending on the paint type, brand, and finish. Our default of 350 sq ft/gallon is a common average.

Should I buy extra paint? ▼

Yes, it's always recommended to buy a little more paint than your estimate. This ensures you have enough for touch-ups later or if you encounter unexpected issues during painting. Leftover paint can also be useful if future repairs are needed.