Paint Calculator | Estimate How Much Paint You’ll Need

Enter the dimensions of your walls, as well as the number of doors and windows, to calculate how much paint you will need. You can also select whether to include the ceiling and the number of coats. Measurements should be in feet.

Note: This is only an estimate. Please contact a professional before placing your order.

Purpose of This Calculator

This Paint Calculator helps you estimate the amount of paint needed to cover your room walls and ceilings based on room size, wall measurements, number of doors/windows, ceiling inclusion, and desired number of coats.

It works for:

• Rectangular rooms
• Square rooms
• Custom-shaped rooms

How to Use the Calculator

Step 1 – Select Room Shape

• Choose the shape of your room from the options:
• Rectangle: Enter different width and height for length and width walls.
• Square: Enter one side length; all walls are considered equal.
• Custom: Add each wall’s measurements individually.
• Click on the desired shape — the selected option will be highlighted.

Step 2 – Enter Wall Measurements

• For each wall, enter:
• Width (or side length for square rooms)
• Height
• For custom rooms, use the “Add Wall” button to include additional walls.
• To remove a wall, click the 🗑 remove button next to the wall.

Step 3 – Subtract Doors and Windows

• Enter the number of doors and windows to subtract from total paintable area.
• Default values:
  • Door: 20 sq ft
  • Window: 15 sq ft
• The calculator automatically subtracts their area from total wall coverage.

Step 4 – Include Ceiling (Optional)

• If you want to paint the ceiling, check the “Ceiling Paint” checkbox.
• The calculator will include ceiling area in the paint estimate.

Step 5 – Choose Number of Coats

• Select how many coats of paint you plan to apply:
• Options: 1, 2, 3, 4
• The calculator multiplies the total paintable area by the number of coats to give an accurate estimate.

Step 6 – Calculate

• Click the “Calculate” button.
• The results display:
• Total Wall Area – sum of all wall areas before subtraction.
• Doors & Windows Subtracted – total area of openings.
• Net Wall Area – total wall area minus doors/windows.
• Ceiling Area – shown if ceiling paint is selected.
• Wall Paint Needed – gallons required for walls based on number of coats.
• Ceiling Paint Needed – gallons required for ceiling (if selected).
• Total Paint Needed – sum of wall and ceiling paint.

Note: The calculator assumes 1 gallon of paint covers approximately 400 sq ft.

Tips

• Measure all walls in feet.
• For better accuracy, round up measurements to the nearest inch or foot.
• Add extra paint for touch-ups or texture differences.
• If your walls are unusually textured or absorbent, consider adding 10–15% more paint.