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MEASURE ONCE. PLAN YOUR PURCHASE.

Room Surface Area calculator.

Measure walls and ceiling, subtract openings, and keep the surfaces separate.

PAINTING

Your inputs

lengthheight

Measurement schematic, not to scale. Use your own dimensions and product specification.

Use measurements from your plan and properties from your chosen product. Any prefilled values are illustrative.

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Where to get this value

Measure this dimension in your plan or on site and use the displayed unit. For irregular shapes, divide the geometry into the supported sections.

Where to get this value

Measure only the area, length or quantity to deduct, in the unit shown. Keep this consistent with the surface being calculated.

Quantity and planning estimate
YOUR ESTIMATE
Room Surface Area Calculator
Net wall area: 800 ft²
Ceiling area: 600 ft²
Openings excluded: 0 ft²
Walls and ceiling: 1,400 ft²
Inputs
Length: 20 ft
Width: 30 ft
Wall height: 8 ft
Total wall openings: 0 ft²
Formula: Walls = 2 × (L + W) × H − openings
Assumptions: Openings are subtracted from the walls once. Ceiling area is listed separately.
Only quantities from supplied dimensions and specifications are calculated.
No material-property reference values are bundled; obtain product values from the selected supplier's data sheet.
Based on supplied measurements and specifications. No design suitability or code compliance is assessed.

Net wall area

800 ft²

Example estimate · update the inputs for your project

How this result becomes a purchase quantity

These are the actual stages returned by this calculation. Stages with the same quantity and unit are shown once. Additional stages are not invented.

  1. Ceiling area: 600 ft²
  2. Net wall area: 800 ft²

Walls = 2 × (L + W) × H − openings

Openings are subtracted from the walls once. Ceiling area is listed separately.

Ceiling area600 ft²
Openings excluded0 ft²
Walls and ceiling1,400 ft²
i

Use your chosen material specification. Quantity does not confirm design suitability.

KEEP YOUR PROJECT TOGETHER

Plan the whole room.

Reuse your dimensions, add the other materials and build a purchase list.

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Formula and assumptions
BEHIND THE NUMBERS

How this calculation works.

Openings are subtracted from the walls once. Ceiling area is listed separately.

Walls = 2 × (L + W) × H − openingsCalculated with normalised units

A worked example

Illustrative inputs only. Product properties and design dimensions are not recommendations for your project.

Length
4 m
Width
5 m
Wall height
3 m
Total wall openings
2 m²

Net wall area: 52 m²

Before you purchase

Use dimensions from your plan and properties from your chosen product. Any design spacing, section or fixing pattern must already be specified.

Method: dimensional arithmetic and user-supplied specifications. Software checks: 2026-10-03. Calculation and review policy.

Check your purchase assumptions

Add opening reveals separately from the wall faceUse average height for walls but slope length for the ceiling

Keep the project moving.

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PaintingPaint Calculator

Estimate paint containers from measured area, coats and the coverage on your product label. See required paint and purchased surplus.

Connected work guides and comparisons

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