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How to Read Plans to Scale


How To Use an Architectural Scale for Floor Plans

Creating blueprints is one of the most important aspects of being an architect. To guarantee your drawings are accurate and thorough, you need to have the right tools handy. One of the most vital pieces of equipment for creating or marking floor plans and blueprints is an architectural scale. Look over this guide to learn more about this essential piece of equipment and how to properly use it.


What Is an Architect’s Scale?

An architect’s scale is a specific type of ruler that is used predominantly in the creation of floor plans and similar blueprints. This tool is typically constructed in a triangular shape to make scaling the drawings easier, though flat models do exist. This type of ruler usually works with a fixed ratio that is determined by the specifications of the project at hand. Scales of this variety are made of a variety of materials including plastic, metal, and wood. Investing in a durable ruler ensures the tool will last a long while.

What Does “Drawn To Scale” Mean?

When something is “drawn to scale,” it means that the drawing has been created to represent the specific proportions of a larger physical space. In the construction industry, a blueprint that has been scaled down uses a small measurement to depict a bigger measurement. For example, a ratio of 1:8 means that the measurements of the drawing are eight times smaller than the real-life measurements.

Steps on How To Read Plans to Scale

Reading a scale is not a task many people can jump into without proper preliminary research. For example, many beginners fail to realize that the scale of a residential floor plan will often utilize a different ratio than that of a commercial layout. This step-by-step breakdown will give you a better idea of how to approach any scaled drawing you may need to use.

1. Determine the Scale.

The first step of using your scale ruler is to figure out the exact scale that is being represented on a drawing. This will typically be written somewhere on the blueprint itself and follow a very basic layout. If you see the ratio listed as ¼” = 1’, it means that one-fourth of an inch on the drawing is meant to depict one foot in the actual space. You may also see this same scale represented as 1:48. Most blueprints will have the ratio clearly marked, though how the numbers are written will depend on the preferences of the architect.


2. Match the Numbers

After you have determined the scale being used, you want to grab your architect’s ruler. Look for the matching number on the scale. If you’re working with a ratio of ¼” = 1’, then search for the ¼” mark. It is important to keep in mind that different blueprints will rely on different measurement units. One side of the ruler will be structured for the imperial system, while another will have the markings common to the metric system.

3. Start at Zero

Once you’ve found the correct number on your ruler, grab your blueprint and place the scale on top. Align the zero on the ruler with the point on the drawing where you plan to begin taking measurements. Make a mark above the zero on the drawing, then proceed with creating your lines.

4. Draw a Blueprint From Scratch

If you’re attempting to draw a scaled floor plan from scratch, you first want to determine whether you’ll be using an imperial or metric scale. Since you’re in control of the scale, try to select a ratio that works best for your needs. The larger the space you’re attempting to depict, the smaller you will need to make the drawing in order to include all relevant components. There will be some trial and error involved, so don’t feel discouraged if you make several mistakes on your first attempt. The more you practice, the more accurate your drawings will be.

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Frequently Asked Questions

Where Can I Buy a Quality Architectural Scale?


Investing in the right gear is key to your success when working with scaled blueprints. Take a look at the variety of equipment available at Engineer Supply and see which architectural scale aligns with the demands of your next job.

What Is the Most Common Scale Used in Architecture?

For residential floor plans, the most common scale used is ¼” = 1’. If you’re working on a commercial blueprint, it is more likely that you will be relying on a scale of ⅛” = 1’. All blueprints should be clearly marked to inform others of what scale is being utilized.

How Many Scales Are Included on an Architect’s Ruler?

On a triangular architect’s ruler, there are usually about 12 different scales included. However, some models limit this to six scales. If you’re working with a flat ruler, there will only be four different scales included.

How Long Does an Architecture Ruler Last?

A ruler used to scale blueprints can last for many years. When picking an architect’s scale, be sure to invest in an option that is made from durable materials like aluminum. Try not to place too much pressure on the ruler, as this can reduce its longevity.

What Are the Lines on an Architect’s Ruler Called?

Traditionally, the lines on a ruler are referred to as marks. However, you may also hear them called “hatch marks.” Each of these marks is meant to represent a different unit of measurement as it would appear along a straight line.

Though using a tool like an architectural scale can seem intimidating at first, a bit of practice will help you get a feel for the process. Review the selection of rulers available at Engineer Supply to discover the perfect fit for your upcoming project.
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