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It is not square at all. It’s a triangle! If you are unfamiliar with this handy tool, you may be surprised by how many speed square uses this small tool has.


I learned about speed squares in a high school woodworking class where I was the only girl. That awkward and quiet teenage girl in a room of all the most popular boys moment had come true. 🤩😩

This is an essential tool for professional builders and DIY enthusiasts. You honestly don’t need much more than this device to do a lot of what you need in woodworking. 

It is a triangular measuring instrument used for various tasks such as measuring angles, marking and cutting rafters, and serving as a saw guide for circular saws. Plus, much more!

I added a few videos in case you are more visual, so feel free to watch the nifty device in action!

This article will explore what makes a speed square special, its features and uses, and provide tips and techniques for utilizing it effectively.

Disclosure: This post may contain affiliate links, meaning I can earn commissions. If you decide to purchase through my links, it is at no cost to you.

What is a Speed Square, and How to use a speed square?

Understanding the Basics – The Speed Square Explained

different sized speed squares

A speed square, also known as a rafter square or carpenter square, is a triangular tool (so not a Square, maybe call it a triangle square??) that combines the functionality of a protractor, square and saw guide. A carpenter square is always handy beside your favorite power tool.

The typical speed square comes in a standard 7-inch (to fit across Two 2 x 4 lumber boards), but there is also a large speed square that is 12 inches. This tool makes 90 and 45-degree angles easy!

Let’s get to know the tool:

  • Hypotenuse – the longest side with markings from 0 to 90
  • Pivot point – The point at one end you can use to rotate to find an angle
  • The Lip – also called the fence runs along the side of a board

The hypotenuse is marked with measurements along the side of the carpenter square, allowing for precise angle measurements and layout.

The pivot point serves as a reference point for various measurements and cuts. Check out this speed square diagram.

diagram of speed square

Who uses It and Why

You’ll find anyone in woodworking and carpentry who will own a speed square set or have multiple speed square tools in the speed square holder on their tool belt. Those who need to build a roof, measure the pitch of a roof, draw a straight line, or do any home improvement project will need a carpenter square. 

It is one of the most versatile measurement tools you will own. When I think of this tool, I always envision my dad’s Swanson speed square. 

“The first square you buy should be a 12-inch speed square.”

Exploring the Different Features

A speed square usually has multiple features designed to enhance its versatility. Let’s look at some carpenter squares features:

  • Built-in ruler
  • Angle finder
  • Protractor
  • Adjustable fence (Some have this)
  • A notch for scribing
  • A cutout for miter cuts
  • Scribe Bar: in 1/4 inch spaced notches
  • Center Line: Find the center of up to 3-inch round stock
  • Built-in Bubble Level

How to Read all the lines on a Speed Square

There are many lines on a rafter square, so understanding how to read measurements from these lines is essential for accurate layout and cutting.

  • Inches: marking and measuring length, depending on the length of the square
  • Degrees: 0-90 determining angles
  • Common: 1-30 – for reading roof pitches and common rafter (in decimeter or meter)
  • Hip-Val: 1-30 – for hip and valley rafters which have different rafters than a common rafter
Hip rafter and common rafter
YouTube Photo Credit – YouTube @HultaforsGroup

You can mark precise measurements by aligning the pivot point and the desired angle on the hypotenuse.

What are all the lines on a speed square
The Big 12-inch Speed Square by SwansonToolCo

Angle Measurements

Measuring and Marking Angles

Measure and mark angles with a Carpenter Square in 2 steps:

  1. Align the pivot point with the edge of the material you want to mark.
  2. Slide the square along the material while keeping the pivot point steady and perfectly square.

Using it as a Protractor

A triangle square is also your built-in protractor to measure and draw angles accurately in 4 steps:

  1. Position the square at the desired angle.
  2. Align it with the degree markings.
  3. Keep the square tight against the material. 
  4. Use the hypotenuse as a guide to draw a line that represents the angle you need.
speed square as a protractor
Todays Homeowner, Measuring an angle

Speed Square for Miter Cuts

A miter cut is made at an angle other than 90 degrees. A triangle square can create precise miter cuts by utilizing its cutout feature in 2 steps:

  1. Position the carpenter square on the material with the desired angle aligned with the edge.
  2. Place the circular saw blade in the cutout, ensuring it follows the angle indicated

Watch this in action in this YouTube video.

Using it as a Saw Guide for Circular Saws

Setting it up as a saw guide

Using a triangle square as a saw guide with a circular saw can help you achieve accurate and straight cuts in 3 steps:

  1. Position the square on the material you want to cut to set it up.
  2. Aligning the saw shoe’s edge with the square’s edge.
  3. Ensure that the square is securely in place before cutting. 

Watch your fingers! 👍🏻

speed square as a saw guide
MakeZine, Use a speed square as a Saw Guide

Making Accurate 90-degree Cuts With a Circular Saw

When using a speed square as a saw guide, it is effortless to make accurate 90-degree cuts in 2 steps:

  1. Position the square perpendicular to the edge of the material.
  2. Guide the circular saw along the edge of the square. 

Creating angled cuts with a speed square and circular saw

A carpenter square can also make angled cuts with a circular saw in 3 steps:

  1. Start by tilting the saw blade to the desired angle using the bevel adjustment.
  2. Hold the square on the material with the desired angle aligned with the edge. 
  3. Using the square as a guide, move the circular saw along the length, following the angle indicated by the square.

Check out this video for some basics and speed square tricks!

How to Measure Roof Angle and Rafter Layout with a Speed Square

To measure a roof angle with a speed square:

  • Make sure to look at the angle from a true horizontal position.
  • Place one end of the carpenter square on the bottom edge of the roof and orient it so that it is perpendicular to the roof.
  • Measure up to where the roof meets the side wall or whatever boundary defines your angle.
  • Note this measurement, then rotate your carpenter square around until you find the same angle on it.
  • Once you have done that, note the measurement on the carpenter square’s scale.

How to use a Speed Square for a Rafter layout

Determine a rafter layout with a carpenter square and a calculator. Rafter layout involves determining the slope of the roof. To Solve for slope, you must understand the following:

  • Span
  • Total Run
  • Unit Run
  • Unit Rise

Check out this video to learn some rafter layout techniques.

4 Common mistakes to avoid when using a speed square 😩


While a speed square is a handy tool, there are some common mistakes to avoid to ensure accurate measurements and cuts.

  1. Not properly aligning the square with the material
  2. Not securely fixing the square in place when using it as a saw guide
  3. Not double-checking measurements
  4. Not ensuring the stability of the square on the material

Benefits of Using an Aluminum

Exploring the advantages of an aluminum

Aluminum speed squares are popular among professionals and DIYers for several reasons.

  • Durability and lightweight
  • corrosion-resistant, making them suitable for various weather conditions. 

Comparing aluminum to other materials

While aluminum speed squares have advantages, other materials are worth considering.


  • More affordable
  • Less durable


  • Excellent corrosion resistance
  • Heavier

Choosing the best aluminum for your needs

When choosing an aluminum speed square, it’s essential to consider factors such as:

  • Accuracy
  • Build quality
  • Additional features like level, etc

Look for a carpenter square with clear, easy-to-read markings to ensure precise measurements. 

Consider the tool’s build quality, overall durability, and additional features that may enhance its functionality. 

Where do I Buy a Speed Square

Speed squares are available at a local hardware store or a large box store like Home Depot, Harbor Freight, Walmart, or Lowe’s.

The online world will have several options with various features. You can find small speed squares, large speed squares, quick squares, speed squares with bubble levels, and probably even a pink one! 🩷

Brands and Options

Speed Square vs. Framing Square

These tools can be a great addition to your tool set but have a few differences.

speed square vs framing square
Speed square versus framing square

Frequently Asked Questions

What is a speed square used for?

Basic uses are determining angles, making square cuts, marking common, hip, or valley jack rafters, and laying out stair stringers.

What size speed square do I need?

A 7-inch and 12-inch speed square is what many have in their toolbag to accomplish most tasks.

What is the best square to buy?

While many speed squares are similar, they have some similarities. Check out the Best Speed Squares.

Can a speed square be used as a protractor?

A speed square can also be used as a protractor. It has degree markings on one of its sides, making it suitable for measuring and marking angles.

How does a speed square help in making accurate cuts?

A speed square can be used as a guide for making straight and angled cuts. It provides a straight edge that allows for precise measurements and ensures accuracy in cutting.

Can a speed square be used for framing?

Yes, a speed square is a commonly used tool for framing. It can help mark and measure angles, making it an essential tool for framing and layout tasks.

How easy is reading the measurements?

Most speed squares have clear and easy-to-read markings, making it convenient for users to read and take accurate measurements.

Can a speed square be used for tasks other than carpentry?

A speed square can be used for tasks other than carpentry. It can be used in metalworking, masonry, and even as a layout tool for general DIY projects.

Is there such a thing as a magnetic speed square?

Some speed squares are designed with a magnetic feature, allowing them to stick to metal surfaces. This can be useful when working with metal or for hands-free usage in certain situations.

What materials are speed squares commonly made of?

A speed square is made of aluminum alloy, which makes them lightweight, durable, and resistant to rust and corrosion. 

How do speed squares work?

Speed squares are multi-purpose measuring tools often used in carpentry. They consist of a right-angled triangle with various scales and features that can help measure angles, mark cut lines, and quickly check 90 and 45-degree angles.


With its wide range of uses and easily-read markings, the carpenter square is invaluable in any woodworking or construction worker’s toolkit.

Don’t underestimate its true potential; once you have this multipurpose tool, you won’t regret investing in one! This may be my favorite tool in my tool belt in the speed square pouch.

The long-term value of a carpenter square could save you time and effort when working on plans or constructing structures.

Get yourself a carpenter square today to make those precise cuts and be the master of the workshop!

The 5 Best Speed Squares for Woodworking and DIY

Check them out
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