Room Area Calculator

Enter the dimensions in one length unit. Area conversions square the length conversion factor. A square metre equals 10,000 square centimetres.

A = LW; P = 2(L + W)
L = 3; W = 4 → A = 12; P = 14

Ellipse inputs are semi-axes, half the full width and height. A kite uses perpendicular diagonals. A regular polygon has equal sides and equal angles; use 3 to 10,000 sides. A trapezoid uses parallel sides and their perpendicular separation.

For identical rectangular rooms, total area is length × width × room count. Material allowance adds the chosen percentage to this area. Perimeter is for one room. For an irregular room, split it into non-overlapping rectangles and add their areas.

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Length unit

m

Length

3 m

Width

4 m

Identical rooms

1

Extra material allowance

0 %

Primary result: Area: 12 m².

• Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
• Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
• When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.

Area alone does not determine material packing, cutting waste or structural suitability. Ellipse, kite and trapezoid perimeter require additional methods or dimensions and are not estimated here. Polygon diagrams above 100 sides are simplified.