Blender is first and foremost a software targeted at artists but sometimes you just want to build your house or some home DIY project and that is when measuring is important. Blender has multiple tools to accurately measure distances and support for multiple units. Another huge topic that needs accurate measuring is architectural visualization and that is an area where Blender really shines.
How to measure in Blender? To accurately measure in Blender, while in edit mode go to the overlay menu in the top right corner. There you will find a section called "Measurement". Check the edge length checkbox to get the length of any selected edge in edit mode.
That is a good start and I use the "edge length" setting in almost every project. However, there is more to the story, and we will dive deeper into Blenders measurement tools and add-ons through the rest of this article.
The first, and most useful tool is already under our belt, but this image shows a bit more clearly where to find it. Next, to the "edge length" setting we also got checkboxes to view face and edge angles as well as face area.
By default Blender measures using the metric system. Meaning meters. In the properties panel under the scene tab, we also find the Units section where we can change what units Blender should use. The other option is imperial. Useful if you are in the US. We also have a setting that is labeled "none". More on that later.
Let's go over the different settings in this unit section and see what options we have. If you are following along in Blender while reading this will be a bit easier to understand.
After the unit system, we have a unit scale. This slider is basically a multiplier of our units. It won't change anything in our scene. The relation between objects in our scene will always be the same. It will just change the numbers that we see. If this is set to 1 and we have the metric system, 1 meter will be viewed as 1 meter. If we change the scene scale to 0.1 we will now see that our 1 meter turned into 0.1 meters.
The scene scale value will not have any effect on simulations. They will still run the same. The only thing the unit system is doing is change what scale our values get in the interface.
Below the scene scale value, we can select the unit that will be used to view our measurements. For each type of measurement we have the usual increments. Meters, centimeters, millimeters and so on. Same for time and mass units.
The length unit is probably the primary reason to choose a unit system but the units for rotation, mass and time also have their place. Mass may not be obvious in a 3D program but it is used to calculate simulations. Likewise, time is used in Blenders animation system and in the Video Sequence Editor. Essentially Blenders video editor.
For any of these, we can also set "adaptive" This means that Blender will display the unit that makes the most sense for the scale of any distance.
There is one more thing that we need to keep in mind. That is object scaling. If an object scale is not set to 1.0 on all axis the measurements will not be correct.
Related content: How and why do we apply scale in Blender?
That is the bulk of how to set the units that we will see in the interface. However, no settings in the Units section will change how Blender works in any way. The units are not used in any calculations.
Remember the "none" option as a unit system. This will use blenders internal system. One could say that 1 blender unit is equal to 1 meter. But that is only true if we stick to the default unit settings. A blender unit is an internal unit that calculations will be based on. Even if we change the units that we see, the blender unit will still be used under the hood.
The important distinction to make here is that it does not matter much what settings you choose in the units section. These can be changed at any time without having an actual effect on your scene. It is only related to what you see in the interface. The importance is rather with the relationships between objects within your scene. Your scene is then relative to any measurement system that you may choose.
Generally, you will not 3D print directly from Blender. Instead, you will export your model as an STL file and import it into another software. The scale will be determined by how the 3D printer software interprets it.
What you need to keep in mind is to model according to some measurement. If it is to meters or centimeters does not matter much but if a distance is supposed to be 1.5cm long and you model it to be 1.32cm long it will be hard to scale it correctly later. But getting the correct length when scaling from 1.5 meters to 1.5 centimeters is not a problem. You just divide the scale by 100. Simple, even math.
The ruler has been renamed measure tool in Blender 2.80. We can find it at the bottom of our tools panel on the right side of our 3D viewport.
If we hove our mouse we get a detailed description of how we can use this tool. When the tool is activated we click and drag in the interface to get a measure. We can du this multiple times to add more measures. If we have multiple measures one of them will be white and the rest will be gray. The white is the current active ruler.
If we press "X" the currently active ruler will be deleted.
To measure an angle, press the middle of a ruler and drag. An angle measure can be turned back into a distance measure if you click the corner and press "X".
Both the ends and the corner of the measure tool can be snapped to a face, edge or vertex if you hold control while moving it. We can also snap the angle.
The last feature is to measure the depth of an object. To do this hold shift while moving the ruler and the other end will run through the inside of the object and snap on the other side.
Another tool that may be less obvious to use for measurement is the grid. By default, the grid is set to 1 meter. We can change this in the overlay panel. At the top of the panel you will find the guide section. Here we can set the scale value of the grid. By default, this is set to 1. Depending on our settings in the unit's panel the scale on the grid may vary. By changing the grid scale we set the grid in relation to our current measurement system.
Related content: How to use snapping tools in Blender
We can accurately move objects to exact measures according to the grid by using snapping. In the 3D viewport header, click the magnet icon to enable it. Then click the snapping menu next to it and set the snapping to increment and turn on "absolute grid snap".
With these snap settings, we can take the object origin and snap it to any intersection of the grid. In edit mode, we can also snap any element such as face, edge or vertex directly to the grid.
What is the Measureit add-on?
The Measureit add-on comes with Blender by default. It can help us to create good-looking visual measures. It is useful both for measuring and to create blueprints or similar where we want the measures to show up in the actual render.