Straightedge Vs Ruler

Wondering about the differences between straightedge and ruler? Are you confused about which one to use for your project? Can we consider both of them are the same tool? This page will answer those questions.


1. Function

A ruler is one of the most common and basic tools used to measure length. You can use it to measure the object’s dimensions be its length, width, and depth.

2. Accuracy of the Graduation

Due to its purpose for length measurement, the accuracy of the ruler graduation is highly important for a ruler to be considered a precision ruler. Again, it depends on the use. If you use it as desk ruler (to draw straight lines), the graduation accuracy may not that critical.

3. Models of Ruler

The ruler is available in different sizes and with different types of measurement marks on it depending on their application and is built using a variety of materials. On the basis of size, graduation, material, and their applications, there are several types of ruler including steel ruler, meter stick, folding ruler, measuring tape, seamstress tape and engineers rulers.

The most commonly used ruler type is a desk ruler which is used by students and engineers for drawing different shapes. It is made using wood or plastic or steel.

The measuring tape is the second most commonly used ruler type. It is mostly made of a metallic strip that is folded in a plastic enclosure. This tool is generally used in construction for measuring the dimensions of objects such as walls, etc. It serves you with graduations in inch, feet, cm, fractions, etc.

Don’t forget about precision ruler. It’s used by machinist, thus considered machinist ruler. It serves you with greater accuracy compared to a desk ruler.

4. The Applications of Ruler

It is being used by students of different grades for their small level measurements and for drawings of geometrical features having straight lines. It is also being used by carpenters and construction workers for manufacturing of dimensionally accurate furniture and for the construction of different surfaces with desired dimensions. It is also used by machinists for the manufacturing of dimensionally accurate parts. Other than measurement, the ruler is also used where straight lines need to be drawn or for straight cutting of papers or similar materials.

5. Calibration of Ruler

To check the accuracy of your ruler, you need to compare it with the more accurate one. Put them side by side, by using the loupe, you can check the how the markings are aligned. The machinist rulers, in this case, will show you a neat marking and graduation lines.


1. Function

Though some models have the same look as rulers, straightedge has a different purpose. The reason for using a straightedge is to check the straightness or flatness of a surface.

2. Models

You can find several models of the straightedge to choose from based on your need. One of the models has a sharp edge.

Typically, the straightedge are not used to measure the length because it doesn’t contain graduation or marking on it. However, some models have graduation as well. Similar to rulers which its main function is for length measurement, but some rulers are made with tight straightness as well like the combination square (certain brand) that its blade has fine straightness.

3. The Applications of Straight Edge

A straightedge is used by architects, woodworkers, metalworkers, engineers and developers in different constructional and industrial projects, where sole reason for its usage is to make sure that different surfaces and lines are straight and does not contain any curves, breaks or splines.

A straightedge does not have the measurement marks so it cannot be used in places where measurement of lines or surfaces is required. A straight edge can also be used to check or control the flatness of a surface.

4. Calibration of Straightedge

Straightedge calibration is about calibrating the straightness. One of the tool for calibration is dial gauge. If the straightness value is not within the agreed tolerance, the straightedge needs for a replacement.



Both ruler and straightedge can be used as assistance in drawing lines due to their edge is straight.


So, it is clear that the main difference between ruler and straightedge is its functions. Ruler makes use of its graduation to measure length or dimension. While straightedge makes use its straight edge to measure straightness or provide straight line/surfaces.

However, some models can cover both these functions. Surely, you can buy this model if the straightness value is within your accepted tolerance.