The Best Combination Square (2024)

I have 10 years of experience in the construction industry, first as a carpenter, then as a foreman, and finally as a jobsite supervisor running multimillion-dollar remodeling projects in the Boston area. During those years, I spent a good deal of time measuring and cutting, and I was never far from a combination square. Over time, I’ve probably owned seven or eight of them, and because of that, I have a pretty good eye for what makes a good one and what makes a not-so-good one. In addition to my work in the trades, I’ve been writing about and reviewing tools since 2007.

A combination square is a useful tool for layout and marking, particularly with any woodworking project. Every carpenter I’ve ever met carries one. At its most basic, the tool gives you a way to draw a line square off the edge of a board. It can also mark one at a 45-degree angle. The ruler slides within the tool, and you can lock it in place with a knurled thumb turn. This design lets you easily mark a specific measurement off the edge of a board (say, if you’re going to cut a notch) or draw a line parallel to the edge of the board. You can also remove the ruler and use it in situations where a tape measure is impractical. This article at Wood Magazine explains even more uses for the tool, from calibrating a table saw to setting the depth of cut on a saw blade.

12-inch models are the most useful. A combo square with a 12-inch ruler can extend a square line a little over 10½ inches, which is enough for most common widths of lumber (for lengths beyond that, you can flip the square to the other side of the board and complete the line). 16-inch rulers are unwieldy, and 6-inch models are too small.

For around-the-house use, a combo square with a zinc body is the best option. It’s reliable and easy to calibrate, and if the ruler bends, replacing it doesn’t break the bank. In contrast, high-end models like the Starrett have cast iron bodies and tempered-steel rulers, making them premium products with laser accuracy, but at over $100, their cost is excessive for home use.

A stainless-steel blade is important. Regular steel blades will rust to the point where the markings become impossible to read. Some models have a coated blade to prevent corrosion, but once the coating chips off, the blade is toast. Getting a stainless ruler is worth the $5 or $6 upgrade.

For our tests, we came down to six finalists, all but one with a zinc body and a stainless-steel ruler. The oddball was the Swanson TC131with its plastic composite body. We wanted to see how it would stack up against models with durable metal. We chose tools based on the manufacturer's reputation as well as on the customer feedback at retailers like Amazon, Home Depot, and Lowe’s. I’m familiar with all of the companies represented, and all are known for quality hand tools.

To test our selection of combo squares, we first confirmed whetherthey provide a perfect 90-degree angle, and we did any necessary calibrations to correct them. We thenused each one during a large garage shelving project, paying attention to overall handling (how easily the ruler slides, the action on the knurled knob, and the ease of flipping the ruler in the base). I also checked each metal ruler for accuracy with an older version of this Lixer Tape Measure Calibration Tool (all of them were well within 1/64 inch of accurate).

Of the six combination squares that we tested, the best for most people is the Irwin 1794469 12-inch Combination Square.What impressed us is the high level of fit and finish that the Irwin offersfor arelatively low price. The edges are evenly chamfered over, and the body has a powder-coated finish to it. The ruler slides easily, and the knurled drawbolt that locks it in place is simple to access and use. Simply put, the Irwin was the combination square we enjoyed using the most. In fact, it was far more polished and professional-looking than other tools that closed in on the $20 mark. With all of my experience using combination squares, I would have guessed it to be at least twice the price, just from the way it handles.

Irwin has a zinc body and a stainless-steel ruler. Neither of the two will rust or corrode over time. Both of these features were common among the better squares we tested, but many inexpensive combo squares have steel blades coated with a protective finish; once the coating chips off (and it will chip off), the blade quickly deteriorates to the point where you can’t read it.

Each of the four edges of the Irwin ruler has a different incremental measurement scale. Three are imperial (⅛, 1/16, and 1/32 inch) and the last is metric (millimeters). The ruler can be removed from the base and flip it so that you can change which scale is on the outer or inner side of the tool, depending on the gradations and precision you’re looking for. Some combo squares have the imperial scale on all four sides. We’ve always found the metric scale useful for measuring metric nuts and bolts. When working in the imperial scale, flipping the ruler in order to move the metric scale out of the way is easy enough.

The Irwin is a very nice tool for the price. Some combination squares, like the much vaunted Starrett, can cost quite a lot, but the differences betweenthe low end and the high endwill likely be lost on the occasional user or DIYer. Starretts have durable cast iron bodies and microscopically precise measurement markings. While they’re popular among serious woodworkers, most carpenters I know opt for a zinc combo square like the Irwin. Such a tool isperfect for all but the most precise work, and if you step on it and bend the ruler, you caneasily replaceit.

Straight from the packaging, the Irwin was a cat’s whisker out of square. It wasn’t much, just a pencil line off. Correcting this was a simple process that took maybe 90 seconds. Learning how to check for square and make an adjustment is worthwhile, and it isn't a big deal at all (this video explains everything). In fact, all but one tool that we tested was out of square upon arrival.

The scribe is pressure-fit and not threaded. Every combination square comes with a small metal scribe stored in the base of the handle. It looks like a nail and can be used to scratch a precise line in lieu of a pencil. On most combo squares, the scribe has a threaded piece that screws into the base to store it securely. On the Irwin, however, the scribe is only pressure-fit into the handle. The connection stays tight and allowed us to remove the scribe quickly, but we’d prefer the more secure connection of a threaded piece. In the end, though, you might never use the scribe.

If the Irwin is unavailable, considerthe Swanson 12-inch Combo Square. The least expensive metal-bodied square we looked at, this tool satisfies the basic requirements (zinc body, stainless-steel ruler). It was also the only combo square we tested that was perfectly square out of the package. Its base isn’t as robust as that of the Irwin, and the level of finish is lower. Slight inconsistencies can be felt along the edges; they’re not severe to the point where they disrupt a pencil line, but their presence is a reflection of the tool's lower price. Ultimately, this slight reduction in quality does not impede the tool's overall function.

Amazon customer feedback for the Swanson currently sits at a decent 4.6 stars out of five, across more than 1,000 reviews. Some negative comments say that the tool arrived out of square—a situation that’s more likely than not. Learning to test and calibrate your combo square is essential to owning one.

The Swanson Savage SVC133, which has a more modern design, arrived significantly out of square. Of the metal squares we tested, it was the lightest model, which none of ourtesters cared for.

Lastly, we looked at theSwanson TC131which has a composite handle and feels very light. With the Irwin and the others priced only a fewdollars more, choosinga tool with amore durable metal base makes more sense.

We dismissed, without testing, any models that had a coated blade instead of a stainless one, including aStanley.

The other option we considered in addition to a combo square is a 7-inch rafter square, the most well known of which is the Swanson Speed Square. Popular with carpenters, these triangular tools can mark any angle from 0 to 90 degrees; they're ideal for complex rafter angles. Most of this added ability will be lost on the non-specialist, but if you use a circular saw, you can use a rafter square as a saw guide for making consistently straight 90-degree cuts (see this image). If you’re getting interested in advanced carpentry, you can learn more about the nearly infinite uses of a rafter square in this booklet, which comes with Swanson’s version of the tool.