Scale and Dimension Planning

Scale planning: how big should the space be?

Scale planning decides the size of a room or building. The simple idea is:

Floor area = number of people × area for each person

A classroom may give each child about 1.5 m², so 40 children need 60 m². A library reading room may give about 2.5 m² per reader. The area for each person depends on what they do: sitting at a desk needs less than working with big machines.

Also think of future growth: if more people may come later, plan a little extra or a way to extend the building.

Drawing scale: shrinking the real size

A plan is a small drawing of a big thing. The drawing scale tells how much it is shrunk. 1:50 means 1 unit on paper stands for 50 of the same unit in real life.

• Real length ÷ 50 = length on paper. 4 m = 400 cm, and 400 ÷ 50 = 8 cm.
• Length on paper × 50 = real length. 7.5 cm × 50 = 375 cm = 3.75 m.

Common scales: 1:100 for whole floors, 1:50 for rooms, 1:20 for details. A bigger second number means a smaller drawing. Always write the scale on the plan, and never measure a printed plan if it was enlarged or shrunk: use the written dimensions.

Dimension planning: body + furniture + clearance

Dimension planning fixes exact sizes of rooms, doors, corridors and furniture places. Three things add up:

1. The size of the body (and what it carries or uses, like a wheelchair or a tray).
2. The size of the furniture or equipment.
3. The clearance, the empty space needed to use it.

Example: a bed 1.0 m wide with 0.6 m on both sides needs a room 1.0 + 0.6 + 0.6 = 2.2 m wide. Use SI units (metres, centimetres, millimetres) and keep one unit through a drawing.

Modular coordination and grid planning

A module is a basic unit of length. Many places use a module such as 100 mm (called 1M) or about 90 cm for houses. Modular coordination means all sizes of rooms, doors, windows and building parts are multiples of the module, so factory parts fit together without cutting.

Grid planning draws a grid of lines at module spacing and places walls and doors on the lines. Benefits: easy drawing, less waste, parts that can be swapped, and easy changes later.

Example: a 90 cm module makes a 3-module room 2.7 m, and a 4-module room 3.6 m.

Layout and circulation

Layout is how rooms and furniture are placed. Circulation is how people move between them: doors, corridors, stairs, lifts.

Good circulation: short and direct paths between rooms used together (kitchen and dining), no path that cuts through a private room, wide enough corridors, clear exits, no dead ends in busy places.

A good test: draw the daily routes of a person with a coloured line. If the lines cross a lot or pass through bedrooms, rearrange the rooms.

Try it: plan your own room

(1) Measure your room length and width and find the area. (2) Draw it on squared paper at 1:50: every 2 cm square on paper is 1 m of real floor. (3) Cut small paper pieces for your bed, desk and wardrobe at the same scale. (4) Move them on the plan and keep 60 cm free beside the bed and a path from door to desk. (5) Check: do all pieces fit with clearance? In the 3D above use the sliders to see how area and plan size change.

Key formulas and definitions

• Floor area = people × area per person
• Length on paper = real length ÷ scale number (1:50 → ÷ 50)
• Real length = length on paper × scale number
• Room size = furniture + clearance on each side
• Grid size = number of modules × module length

Worked examples

Common mistakes

• Reading 1:50 the wrong way. It means 1 on paper = 50 in real life, not the opposite.
• Forgetting to convert units: 4 m is 400 cm before dividing by 50.
• Adding only the furniture size and forgetting the clearance.
• Drawing a path that cuts through a private room to reach another room.