Sisämittaa

Sisämittaa, literally “internal dimensions” in Finnish, refers to the distance between interior surfaces of an object or space. It denotes the usable or product space inside, excluding wall thickness, trim, or any enclosing frame. The term is commonly used in architecture, cabinetry, furniture design, packaging, and shipping. It is contrasted with ulkomitat, the external dimensions measured on the outside of the object.

Measurement and conventions: Sisämittaa are typically described as length (or width) and height (or depth). In a room, interior dimensions are measured between finished interior surfaces, taking into account built-in fixtures and irregularities. In enclosures or furniture, the inner space results from subtracting the thickness of walls from the outer dimensions. For a simple box with uniform wall thickness t on all sides, the inner width equals outer width minus 2t, inner height equals outer height minus 2t, and inner depth equals outer depth minus 2t; real-world designs may differ due to back panels, shelves, or openings.

Units and tolerances: The metric system is standard in most contexts, using millimeters or centimeters. Some sectors may use inches. Tolerances describe manufacturing variation and should be specified when precision matters for fit, clearance, or capacity.

Applications: Knowing sisämittaa helps determine whether equipment or components will fit, estimate usable capacity, plan storage or shelving, ensure door clearance, and align parts during assembly.

See also: ulkomitat, tilavuus, toleranssi.