Johnson Level & Tool 12-Inch Combination Square Review

Johnson Level & Tool Combination Square

Quick Take

It’s easy to recommend the Johnson Level & Tool 400 EM-S 12-Inch because it packs in some of the best value of the models we’ve come across, all without sacrificing build quality.

Johnson Level & Tool 400 EM-S 12-Inch
  • Imperial and metric rule
  • Smooth sliding rule
  • Up to 1/32” scale
  • Dual measurement scales take some getting used to when marking lines
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Alternatives to consider

If you want a combination square with an etched rule: The iGaging 12-Inch 4r may stand the test of time better than the Johnson Level & Tool model with its etched rule. This is also a great pick if you want a rule that goes up to 1/64”. If you want both a 6-inch and 12-inch combination square in one package: The Irwin 6-Inch and 12-Inch Combination Square Set is a great budget-friendly option when you’re looking for a 6-inch and 12-inch combination square in your shop.

Features overview

The Johnson Level & Tool 400 EM-S 12-Inch features a dual-purpose, stainless steel rule with both an imperial and metric scale. One side of the blade includes millimeter and centimeter measurements, while the other edge features a 1/8″ and a 1/16” scale. Flip over the combination square and you’ll see the same metric scale, but the inches are on a 1/32” scale. This versatility makes the Johnson Level & Tool 400 EM-S 12-Inch a great option when needing to strike precise measurements for woodworking projects. The combination square’s anvil is made of heavy-duty cast zinc with a chip-resistant black coating. The anvil also includes your typical bubble level and a scratch awl at the base. The feature that most impressed us when testing the Johnson Level & Tool 400 EM-S 12-Inch is the smoothness of its rule and knob.
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Pictured: The anvil, bubble level, scratch awl and rule. The anvil and components come apart in seconds and the rule can be slotted back into place easily. Credit: Nathan Hamilton
Even the best combination squares have a tendency to pinch the rule when loosening the knob and sliding the rule in place, but this model has one of the smoothest sliding rules of the woodworking squares we tested. What’s more, the knob has a better feel in the hand and is smoother to loosen and tighten than many combination squares that are double the price of the Johnson Level & Tool 400 EM-S 12-Inch. Another standout feature that amps up the build quality is that the rule has etched markings. Compared to stamped markings, etched ones will take a beating without wearing down quickly. This is a rare feature at this price point. RELATED >> How to use a combination square


The Johnson Level & Tool 400 EM-S 12-Inchcan typically be found for just over $10 online. That’s a bargain-bin price for a combination square. We had our doubts before testing this model, especially when it comes to build quality, squareness and accuracy. But those worries quickly disappeared when unboxing the Johnson Level & Tool 400 EM-S 12-Inch and putting it to work. Simply put, this combination square packs in the quality and versatility you’d expect in a higher-priced model, but it comes in at a fraction of the price.


  • Do Johnson Level & Tool combination squares have a warranty?

    The Johnson Level & Tool 400 EM-S 12-Inch Combination Square includes a one-year warranty that covers defects in workmanship.

  • Does Johnson Level & Tool make good combination squares?

    In our testing, we found that Johnson Level & Tool makes some of the best combination squares for the money. The build quality tends to beat competing combination squares at the same price point and higher. Accuracy was also not an issue in our testing when marking lines at 45-degree and 90-degree angles using the CNC-machined anvil and stainless steel rule.

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Nathan Hamilton
Nathan Hamilton is the founder of DIY Gear Reviews and a recognized expert in the home and DIY space. He has over 200 bylines covering topics such as power tools, hand tools, and woodworking. Nathan is the strategic director for DIY Gear Reviews, deciding everything from the content covered to designing the testing methodologies for lab-tested reviews. He can be emailed at


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