PangPang ToolsIrregular floor area: calculate L-shapes and subtract openings
A floor plan is rarely one neat rectangle. L-shaped rooms, attached spaces, columns and openings require a clear distinction between areas you add and areas you subtract before you can trust the final measurement.
Calculate areas with added and excluded regions
Start with gross area and net area
An outer rectangle measuring 10m by 8m has an area of 80m². If a 2m by 2m internal region must be excluded under your project’s measurement rules, subtract 4m² to obtain a net area of 76m².
What counts as an excluded area depends on the job. A floor-finishing quantity, a paint measurement and a contractual floor area may follow different definitions, so establish the purpose before calculating.
- Gross area = sum of valid added regions
- Net area = gross area − valid excluded regions
- Check that no region is added or subtracted twice
An L-shaped floor: subtract the missing corner
One simple technique is to start with a surrounding rectangle. If the overall dimensions are 10m by 8m and a rectangular 4m by 3m corner is missing, the area is 10×8−4×3 = 68m².
This works when the missing corner is truly rectangular and sits entirely within the outer rectangle. In the PangPang Tools easy input, choose the L-shape and enter outside dimensions A and B plus missing-corner dimensions C and D.
- Outside rectangle: 10×8 = 80m²
- Missing corner: 4×3 = 12m²
- Remaining L-shape: 68m²
Two rooms and a column: an additive example
Suppose Room A is 6×4m and Room B is 3×4m, with no overlap. Their combined area is 24+12 = 36m². If one 1×1m column region is excluded by your measurement rules and lies inside the added footprint, the net area is 35m².
Use Add section and Exclude section in the easy area interface. It handles rectangular, triangular, circular and L-shaped zones, but easy mode does not automatically detect overlap. Check that the regions do not double-count one another.
- Room A: 24m²
- Room B: 12m²
- One excluded column: 1m²
- Net area: 35m²
When a shape cannot be divided into rectangles
The Draw by dimensions mode lets you enter successive directions and lengths. For example, right 10m → down 8m → left 10m, then close the final edge to obtain an 80m² rectangle. The typed segment lengths are used as entered rather than rounded by pointer snapping.
For a simple polygon defined by coordinates, the shoelace formula computes its area from the ordered vertices. The drawing mode rejects crossing edges and overlapping completed regions and checks that excluded polygons lie within an added area. You must still verify the measurements against the actual plan.
Net floor area is not always a material order
Material quantities need additional assumptions. Tile purchases depend on tile size, grout spacing and waste; flooring needs cutting allowances; concrete volume requires a thickness. Use the area as one input rather than the final ordering quantity.
Pay attention to units. The tool can accept metres, centimetres or millimetres in the easy input and converts the result to square metres. For example, 2,000mm equals 2m, not 2,000m. Confirm plans and measurement specifications before procurement.
Related tools
Use the tools to verify the steps against your own files or text.
References and scope
These are independent reference links, not an endorsement, certification, sponsorship or affiliation by the cited institutions. Rules, rates and technical standards may change; verify the latest source and your actual conditions.