Combination Square vs Speed Square: What’s The Difference?

Ever stood in your workshop, scratching your head, wondering if a combination square or a speed square is the right pick? You’re not alone! I’m here to break down the differences between these two.

Types of Squares

We have quite a few types of squares to choose from, and the squares we choose will be, to an extent, project- or work-specific.  The shop woodworker, for instance, might not need a rafter square, while the contractor who builds houses would.  

Here are a few of the squares you might choose for your project or job:

• The try square.  This is about as basic a square as you will find.  Measure, mark, and confirm the square of a piece – that’s about it.  You “try” how square a piece is, and thus the name.  You want the face and edge of your piece to be straight, flat, and square and the try square is the tool for the job.
• The miter square.  We mentioned math and the common presence of 45-degree angles in our shop work, and the miter square is the one we each use here.  Most are made to measure and mark 45-degree angles and also 135-degree angles (90 + 45 = 135).
• The speed square.  This square is also called the rafter square we mentioned earlier, and it’s a multi-purpose square.  It is not to be confused with a roofing square or a framing square, although a framing square is also used for rafters, but each is a different animal.  The speed square is common for measuring out rafters and stair stringers, those cut-out 2 x 6 lengths that steps and risers are attached to for stairways.  It’s a good layout tool to have in your shop, and its triangular shape and markings make it easy and speedy to use.
• The combination square.  This layout tool is commonly seen and used in most woodworking shops because of its versatility and ease of use.  It is a steel ruler that slides through a protractor head that is easily adjusted and set on the ruler at the desired measurement by a lock bolt.  You might remember from your high school geometry class that a protractor is a device used to measure angles.  In the case of the combo square, the protractor head has one side that is 90 degrees against the ruler and another that is 45 degrees against it.  

There are other types of squares, but that’s enough to draw some distinctions between the more common ones apt to be found in shops and on job sites.  We want to look a little closer at the last two for this article.

The Speed Square and Its Talents

This triangular tool is used by carpenters and contractors for a variety of purposes for marking out.  Its uses include those that other squares are suitable for, too, making it a versatile addition to your shop.

The base of a speed square has a slight flange that you can put up against your woodpiece’s edge, allowing you to mark a cut line that will be perfectly square to the edge of the piece.  You can also mark a 45-degree miter line.  The speed square is also used to serve as a fence for crosscutting.

The diagonal on the triangular tool includes markings for laying out angles for rafters, roof trim, and stair angles on a stringer.  Beyond that, its uses might include laying out perpendicular cut marks and angles.  It is very accurate in its use, and measurements are easy to follow with black gradation markings against a usual heavy-gauge aluminum that is die-cast for increased accuracy over laser etching.

It was invented in 1925 by Albert Swanson, who founded the Swanson Tool Company for its manufacturing.  In essence, the speed square is 5 squares in 1 tool:

• Try square
• Miter square
• Saw guide
• Line scriber
• Protractor 

Speed Squares commonly come with black gradation markings for common, hip, valley, and jack rafters.  After saying that, we probably ought to explain what that means for those of you who have not done any roofing work (a difficult but enjoyable summer job while in college, along with driving heavy equipment on the job site).

Hip rafters are used when building hip roofs and variants like mansard roofs.  Their difference from the standard rafter is their 45-degree angle to the ridge board.  It’s the diagonal angle and downward slope that gives that distinctive shape.

Common rafters are simply what the name implies.  They’re the main support rafter of the slope between the eaves (the edge of the roof that overhangs the house’s outer wall) and the ridge.

Anyway, the speed square gradations can help you mark all of these angles and features and do it well.  Measuring, marking, and confirming right angles on any board, marking 90-degree angles, marking 45-degree angles, marking 135-degree angles, and all of that roof “stuff” makes the speed square one you will want to have in your shop.  

They come in several sizes, and a 7” speed square can also fit easily in your apron pocket.

Speed squares are not especially expensive.  Ranging from as little as around $10 for a 7” Swanson to around $25 for a 12” model, there really is no budgetary excuse for not having one in your shop.

We turn to one of our favorite resources, This Old House, for a simple video on speed squares.  

See it in action with the crew and learn a little bit about its use.

The Combination Square and Its Talents

When it comes to talent and versatility, you’ll be hard-pressed to find one more so than the combination square.  As we noted earlier, it’s a steel ruler (a removable blade) that slides through a protractor head.  The head can be adjusted and moved along the ruler to your desired measurement and locked into place with a lock bolt.  

This combo square can be used to measure both inside and outside angles.  It’s also a marking device, a miter square, a try square, and a plumb all-in-one tool, and the ruler can be used as a simple straight edge for any purpose as well.  Heads will also include a simple bubble level that will indicate…well, level.

The ruler is calibrated as any other ruler and is usually broken down into inches, eighths, sixteenths, and thirty-seconds.  The ruler has a center slot that allows the head to slide along easily and smoothly once the lock bolt is loosened.  

One side of the head is at 90 degrees to the ruler, and the other side is at 45 degrees.  The head is wide enough on either side of the ruler to allow butting it up against the piece being measured/marked tightly enough to maintain the accuracy of the 90-degree and 45-degree angles.

We consider the combination square the most versatile measuring device in our shop and would not be without it.

You can spend as little as $11 – $12 for a decent 12” combo square and less for a 6”, or you can break the bank and go for a Starrett 12” for around $150 and less for a 6” model.  The Starrett will last your lifetime, though, due to its quality build (considered the best in the industry) at their manufacturing facility in Massachusetts.  

There are a variety of heads to choose from, too, among the many brands, each performing their tasks in different ways to measure different aspects of your woodworking project.  The heads are interchangeable, of course, simply by loosening the lock bolt and removing one from the ruler, and sliding another one on.

Here’s a beginner’s lesson in the use of a combination square, and we think there may even be some experienced woodworkers who might learn something they haven’t done yet with their combo square.

Should You Have Both a Combination Square and a Speed Square In Your Shop?

These two squares do not cancel each other.  Each has its place and use in the woodworking shop, and it’s not a question of one over the other.  Prices are not so high for either that you can’t afford to have both.  We’re sure you will find uses for each that will make you glad you have each.

Whether you choose from a 7″, an 8″ or a 12″ speed square or a 6″, a 12″, or a 24″ combination square, and their corresponding prices, each will have a use that makes having at least one of each worth it.

Square is everything in woodworking, as we said. And we do want to be hip.

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Last update on 2024-12-01 / Affiliate links / Images from Amazon Product Advertising API