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CONSTRUCTION CALCULATOR

Paint Calculator

Estimate paint from a room or known net area, product coverage and coats. Include a ceiling or measured opening deductions, then round to your actual container size.

Calculator

Measurement systemSwitching units converts dimensions, areas, coverage and container size. Gallons are US gallons.
ft
ft
ft
ft²
Enter the area before multiplying by coats. Exclude openings and include any ceiling you want to paint.
Each door deducts 21 ft² (about 1.951 m²); actual sizes are not entered here.
Each window deducts 15 ft² (about 1.394 m²); actual sizes are not entered here.
ft²
ft²/gal
Use ft² per gallon in imperial mode or m² per litre in metric mode.
gal
Use the actual can or bucket size. Units convert with the measurement system.
Advanced options
USD
Labels amounts only; no exchange-rate conversion.
YOUR RESULTS
Paint required1.505 gal
Containers to purchase
2
Net surface area
301 ft²
Area across all coats
602 ft²
Door and window area
51 ft²
Paint purchased
2 gal
Paint above calculated need
0.495 gal
Paint container cost
60.00 USD

Required volume uses net area, coats and the coverage you entered. The order rounds up to complete 1 gal containers. Cost uses that container count.

Page guide

Wall area, coats, and paint coverage

Net surface area is multiplied by coats and divided by product coverage. Containers round up to the size you enter, and cost uses whole containers. Purchased volume can exceed calculated need because of packaging.

To check the rectangular area of a wall or opening separately, use the Square Footage Calculator before subtracting openings or applying paint coverage.

The formula

Room area = 2 × (length + width) × height − openings + optional length × width ceiling. Paint = net surface area × coats ÷ coverage. Containers = ceiling(paint ÷ container size). Cost = containers × container price.

Standard deductions are 21 ft² per door and 15 ft² per window, or their metric equivalents. Measured opening area replaces those deductions. Known net area is used directly. One US gallon is 3.785411784 litres.

A 12 ft by 10 ft room

With 8 ft walls, one standard door, and two standard windows, net wall area is 301 ft². Two coats cover 602 ft²; at 400 ft² per gallon, that is 1.505 gallons, so plan for two whole gallons.

How to use this calculator

  1. Choose room dimensions or a known net surface area. Changing systems converts dimensions, areas, coverage and container size.
  2. For room entry, use standard opening counts or your measured opening area; select Include the ceiling when needed. Enter coats and the product coverage.
  3. Set the actual paint container size. Review required volume and containers, then enter price and currency under Advanced options for the material subtotal.

Use the product label for coverage

Paint coverage changes with product, surface texture, color change, application method, and porosity. Replace the default with the manufacturer's figure.

Primer and finish paint can have different coverage. Calculate them separately when both are required.

Opening deductions are standardized estimates

Standard counts use fixed planning areas; actual opening dimensions vary. Choose Measured total opening area for unusual windows, glass walls or double doors.

Known net area lets you total several surfaces before entering them. Include any desired ceiling area in that total; room-only ceiling and opening controls do not apply to net-area mode.

Assumptions & limitations

What this calculation assumes

  • Room mode uses four walls of equal height; known-area mode uses your measured total.
  • One coverage rate and container size apply to this order.
  • Gallons refer to US gallons; coverage uses ft² per US gallon or m² per litre.

What to keep in mind

  • Trim, primer, surface texture and application losses are not separately modeled.
  • Real coverage can differ from the product estimate.
  • Ceiling entry uses the same product and coats as the walls; calculate separately if they differ.

Common questions

Does the estimate include the ceiling?

Select Include the ceiling in room mode. For known net area, add the ceiling into your measured total. Use a separate calculation when the ceiling product or coats differ.

How do I count five-gallon buckets?

Set Paint in one container to 5 in US mode. Container count rounds the required paint up to complete five-gallon buckets.

Can I measure my doors and windows?

Yes. Choose Measured total opening area and enter their combined area. This replaces the standard counts.

Sources & further reading

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