Paint Calculator

How to Use This Paint Calculator

This calculator estimates paint quantity using accurate room dimensions and adjustable project settings. Follow each step carefully to ensure reliable results.

Step 1: Select Measurement Unit

Choose Feet or Meters before entering dimensions. Use the same unit you used during measurement. Switching units automatically converts values.

Step 2: Enter Room Dimensions

Input the room length, width, and wall height. Measure from finished floor to ceiling. Use precise wall-to-wall measurements. Do not estimate.

Step 3: Set Number of Coats

Select the total number of paint coats required. Most repaint jobs require two coats. New drywall or bold color changes may require additional coverage.

Step 4: Add Doors and Windows

Enter the number of doors and windows in the room. The calculator automatically subtracts standard surface areas to prevent overestimation.

Step 5: Include Ceiling (Optional)

If the ceiling will be painted, enable the Include Ceiling option. The tool calculates ceiling area separately and adds it to the total paintable surface.

Step 6: Adjust Advanced Settings (If Needed)

Open Advanced Options to refine your estimate. You may:

• Select surface type for texture or new drywall adjustments
• Modify waste factor based on job conditions
• Adjust manufacturer coverage rate per gallon
• Enter cost per gallon for budget calculation
• Choose 1-gallon cans or 5-gallon buckets
• Include primer if surface preparation is required

Step 7: Review Results

Click Calculate to generate results. The calculator displays:

• Total paintable area
• Required gallons (rounded to purchase units)
• Equivalent liters
• Recommended number of containers
• Estimated material cost
• Primer quantity, if selected

Review all values before purchasing materials. Professional practice recommends rounding up slightly to ensure full coverage and allow for touch-ups.

How to Measure for Paint

Start with simple measurements. Measure the wall height from floor to ceiling. Then measure the full room perimeter. Add all wall lengths together and multiply by the height to get total wall area.

Next, subtract areas that you will not paint. A standard interior door covers about 21 square feet. A standard window covers about 12 square feet. Multiply the number of doors and windows and subtract them from your total.

If you plan to paint the ceiling, measure the room length and width. Multiply those two numbers to calculate ceiling area. Add this value to your wall total.

Most interior jobs require two coats for proper color depth and durability. Dark colors, bold shades, or fresh drywall may require an extra coat.

Taking accurate measurements prevents overbuying or running short during the project.

Coverage Guide

Most standard interior paints cover about 350 square feet per gallon per coat on smooth, previously painted walls. Actual coverage can vary depending on surface condition and application method.

Textured walls absorb more paint and may require around 10% additional material. New drywall surfaces can require up to 15% more paint, especially if primer is not applied first.

Always include a small waste margin. Rollers, brushes, and natural surface absorption reduce effective coverage. A 10–15% waste factor helps prevent material shortages during the project.

When in doubt, round up your total gallons. Extra paint allows for touch-ups and future maintenance. Store leftover paint in a sealed, clearly labeled container.

Accurate coverage planning controls costs and prevents delays during your painting project.