Woodwork
Door paintable area (leaf, edges and frame)
- where
- leaf face area, one side (m²)
- surface factor (1 flush, more for panelled)
- door leaf height (mm)
- door leaf width (mm)
- area per side including frame (m²)
- frame or lining girth painted per side (mm)
- total area for the door (m²)
- sides painted
- door thickness (mm)
Explain this equation
Works out the paintable area of a door, its edges and the frame or lining, for pricing and paint quantities.
The face of the leaf is height times width, with dimensions converted from millimetres; panelled doors have mouldings that add surface, which the factor k allows for. The frame runs up both sides and across the top, 2H + W, and its painted girth per side gives its area. The leaf edges run the same way, times the door thickness.
Rectangle areas plus strips along the frame run.
Sense check: a standard 1981 × 762 mm flush door with a 100 mm lining girth, both sides, is about 4.1 m².
Watch out: panelled doors can have 20 to 50% more surface than a flush door; adjust k to suit.
Works out the paintable area of a door leaf, its edges and the frame or lining, from the door size.
Enter your values to see the result.
Good to know
The common UK internal door is 1981 × 762 × 35 mm (metric doors are 2040 mm high and 40 mm thick). With about 100 mm of frame girth per side this gives roughly 2 m² per side. NRM 2 measures the area actually covered and frames edge to edge over stops and architraves, so for panelled or moulded doors raise the surface factor k to allow for the extra mouldings. Edges are counted once (two long edges and the top).
Common mistake
Forgetting the edges and frame. On a standard door they add about a third to the leaf area.
Limits
Rectangular doors. Glazed doors: subtract the glass with the window calculator. Architraves are in the skirting and architrave calculator.
Sources
- Howarth Timber, UK door sizes (imperial 1981 × 762 × 35 mm; metric 2040 mm high, 40 mm thick)
- RICS NRM 2 Detailed measurement for building works, Work section 29 Decoration (area or girth measured is that covered; frames measured edge to edge; ≤ 300 mm and > 300 mm girth; radiators by type)
- Geometry: rectangle and cylinder surface areas, prism volumes
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.