Floor plan symbols: in short
On a floor plan, thick solid bands are walls, a gap with a quarter circle is a door and the way it swings, and a thin rectangle in a wall is a window. Lines with short ticks at both ends are dimensions, and text in a room gives its name and area.
A plan with every symbol
This room is drawn by the same code as every plan in Squaremetry. Each symbol below points to something you can see here.
The symbols, one by one
| Symbol | What it means |
|---|---|
| Thick dark band | A wall. Outside walls are drawn thicker than inside walls, here 6″ against 4.5″. |
| Gap with a quarter circle | A door. The straight line is the door, the arc shows which way it swings and how much room it needs. |
| Thin light rectangle in a wall | A window, or an opening without a door. It sits in the wall, so the wall line stops around it. |
| Line with ticks at both ends | A dimension. The number in the box is the length between the ticks. |
| Name and number in a room | The room name in capitals and its area, measured inside the walls. |
Electrical symbols
An electrical plan adds a symbol for every outlet, switch and light to the floor plan. In feet, Squaremetry draws them the US way, as below; a dashed curve shows which switch controls which light.
| Symbol | What it means |
|---|---|
| Circle with one line through it | An outlet (receptacle). Two lines: a duplex outlet. Three lines: a range or dryer outlet. |
| S, S3 or SD | A switch, a 3-way switch (two switches on one light) or a dimmer. |
| Circle with four short ticks | A ceiling light. A circle in a square is a recessed light. |
| Two circles with a dot | A smoke alarm, on the ceiling. |
| Circle with a T | A thermostat. |
| Dashed curve | A switch leg: the light that switch controls. |
Plumbing symbols
Water and drains are drawn as lines in their own color: cold water blue, hot water red, drains dashed. Fixtures such as the tub, toilet and sink are drawn from above at their real size.
| Symbol | What it means |
|---|---|
| Circle with a zigzag | A water heater. |
| Square with three lines | A floor drain. |
| Circle with a filled dot | A soil stack: where the drains go down. |
| Box with an M | The water meter. |
Reading the dimensions
On a Squaremetry plan the width runs under the drawing and the depth along the left. Both are measured to the outside of the walls, so they include the wall thickness.
The area in a room is measured inside its walls. That is why the rooms added up are always a little less than the outside size of the house.
Scale
A plan to scale keeps every length in proportion. A printed Squaremetry report in feet uses 1/8″ = 1′ on Letter paper: one inch on paper is eight feet in the house. In meters it uses 1:100.
How to read a floor plan in four steps
- Find the front door: a door in an outside wall, often with the widest opening.
- Follow the doors from room to room to see how you walk through the house.
- Read the room names and areas to see which rooms are large and which are small.
- Check the dimensions outside the walls for the size of the whole floor.
Figure 1. One floor of 25 × 17 ft. The rooms add up to 425 sq ft.
About this page · Written by the Squaremetry team. Last checked on September 27, 2026. Found a mistake? Send us a message.