If you’re new to working with Unreal Engine there is a lot of up-front information you’ll need to know before you get too far into production. One of these ‘must-haves’ is a solid grasp of how the engine defines its units of measurement.
Unreal Engine 4 and 5 use the Metric System and centimeters as its default unit for measuring distance. This is a departure from previous iterations of the engine where one ‘Unreal Unit’ (or ‘uu’) was 0.75 of an inch in length. The size of the modern Unreal Unit can be changed in the project settings.
By default Unreal uses centimetres for distance and degrees for measuring orientation.
A solid understanding of how scale and measurement work inside your engine is a practical necessity. This is especially true if you’re also using external software packages like Blender or Maya which have their own measurement/scale settings which may not always align with Unreal.
Before we get too far, let’s define a few terms which will make it a lot easier to break things down.
The Unreal Unit
An Unreal Unit is a generic term used to describe the unit of measurement that Unreal Engine uses to calculate a range of metrics including distance, time, velocity, and more. This can be different from project to project so it’s important not to assume that 1uu will always be the same when migrating assets.
This table shows the default value for an Unreal Unit across the most commonly used types of measurement. If the one you’re looking for doesn’t appear you’ll probably find it on this far more comprehensive list from the official documentation.
| Type of Measurement | Unreal Unit |
|---|---|
| Distance/Length | Centimeters |
| Mass | Kilograms |
| Time | Seconds / Minutes |
| Angle | Degrees |
| Speed/Velocity | Meters Per Second |
| Temperature | Celsius |
| Force | Newtons |
The most common type of measurement you’ll likely be working with is distance/length. Here are some quick conversions between common units of distance measurement and the default Unreal Unit.
| Distance | Distance in default Unreal Units |
|---|---|
| 1 centimeter | 1 unreal unit |
| 1 meter | 100 unreal units |
| 1 kilometer | 100,000 unreal units |
| 1 inch | 2.54 unreal units |
| 1 yard | 91.44 unreal units |
| 1 mile | 160,934 unreal units |
| 1 light-year | 946,073,047,258,080,000 unreal units |
Changing Unreal Unit size
There are several ways to change the size of the Unreal Unit. The most common (and practical) is via the project settings. Under the Editor heading is an ‘Appearance’ section, which contains two checkboxes and several dropdowns. These let you change the unit size for each type of measurement separately.
The two checkboxes at the top will tell Unreal how you would like your values displayed. By checking them both you’ll be able to always see what units you’re working in. By default it will only show them where applicable, and not on any component transforms. I like to keep them both checked.
You can change the size of your project’s uu by selecting a new measurement from the dropdown menus. You can pick from a range of common sizes in both Metric and Imperial systems.
These settings can also be changed directly in the DefaultEditor.ini file, which can be found in your project’s config folder.
One limitation to these settings is that the engine doesn’t allow you to define your Unreal Unit size with just any arbitrary number. This means that if you wanted to experience what it was like working in the Unreal Development Kit and set your uu distance to .75 of an inch, you’re out of luck.
To be fair, this is probably for your own good.
Keep in mind
You should think carefully before moving away from the default Unreal Unit size. Centimeters work best for your average project, and a lot of the default values throughout the engine expect you to be operating in those. If there is a scale mismatch in your art pipeline I would highly recommend tailoring your other software packages to match Unreal if at all possible.
That said, changing to a different unit of scale may be completely justified. You know your project better than me! Just know what you’re getting into when you stray from the default settings.
Adjusting unit size in VR
The consequences for irregular or incorrect scale are far more significant in a virtual reality project. Mismatches in the dimensions of your world can cause severe motion sickness and dizziness in your players. Moreover, when looking at your game world in VR it’s far easier to notice when/where the scale is incorrect. Depth perception makes the discrepancies obvious.
If you’re developing your project for VR you’ll want to know about an important parameter in your map’s world settings called World to Meters. Altering this setting is an easy way to globally scale the world in relation to your player.
By default, World to Meters is set to 100 as it expects your project to be using centimeters, and therefore there would be 100uu in a meter. If you wanted to half the apparent size of the player in relation to their world, you would set this value to 50. The smaller the number, the smaller your player will appear.
World to Meters can also be set at runtime to make the player grow/shrink, but be careful. Playing with this setting can quickly make your players feel sick!
Adjusting your grid settings
The grid is a marvelous tool to quickly check the distances between objects. Unfortunately, unlike the details panel it won’t update when the size of your project’s Unreal Unit is altered. This means that even if your project is set to meters, your grid will still operate in centimeters. This can naturally lead to a lot of confusion.
Inside your Editor Preferences, the Viewports menu includes a section on Grid Snapping which will give you a little more control. This includes options to set the snap divisions for translation, rotation, and scale.
The restrictive design of the grid is indicative of Epic’s expectation that most Unreal Engine projects will use the centimeter as their standard unit of distance.
The Measuring Tool
One feature that isn’t mentioned a lot, but one that can prove invaluable (especially to level designers), is the Measuring Tool. Although it only works in the orthographic camera views (which are accessed by clicking the two overlapping rectangles button in the top-right of your viewport), it can be used to draw a temporary line between two points on the grid to quickly and easily find the distance between them.
To use the Measuring Tool, middle-mouse click anywhere in the viewport and drag your cursor to draw a line. Your cursor will automatically snap to the nearest point on your grid.
The Measuring Tool inexplicably uses an entirely separate unit of measurement to your project’s Unreal Unit size. By default it is set to centimeters, but you can change it to meters or kilometers in the Editor Preferences, under the Viewports/Look and Feel subheading.
Common size recommendations
Here are some examples of the default size of common actors that you’ll find in the engine’s project templates and starter content. You can change these of course, every game is different, but they provide a good indication of the kind of scale Unreal expects out of the box.
| Actor/Object | Dimensions |
|---|---|
| Static Mesh Plane | 100cm2 |
| Static Mesh Cube | 100cm3 |
| BSP Box | 200cm3 |
| Box Trigger | 80cm3 |
| Post-Processing Volume | 200cm3 |
| Empty Character | 176cm |
| Third Person Character | 192cm |
| VR Character | 180cm |
Third-party tools
Giving developers the freedom to define their own space inside Unreal is a popular field for those in the community creating editor tools. There are many plugins and asset packs out there that will open up further functionality that can help you create your levels. Here are some I’ve found useful and/or educational.
Distance Measuring Tool
There are several tools on the marketplace for measuring the distance between objects, and a lot of the time they try to overcomplicate things with too much information. I like the Distance Measuring Tool because it’s fast, simple, and doesn’t get in the way.
Level Design Assistant
A more comprehensive package that has a lot of features for level designers, including layout, scaling and measurement tools. Overall the package is quite an overhaul of your default editor environment, but if you’re serious about level design or environment art it’s worth checking out. It’s free, after all!
Make your own!
If you’re at all interested in making your own level-design tools to speed up your workflow (and if you’re into technical art, I hope you might be!) this is a really good area to start.
Mapping the distance between two objects and/or the length of a spline serve as a great introduction to Blueprint, Unreal’s visual scripting language. If you’re keen to learn more about this area, jump over to my tutorial on how to create your own distance measurement tool. I’ll take you through the entire process!
Final tips
I hope this guide has helped you understand how scale and measurement work inside Unreal. Here are a few final tips or tricks which may come in handy.
- Irrespective of the scale of your Unreal Unit, you can move objects in the details panel with any unit of measurement you like. All you need to do is type it into the text field and Unreal will translate it for you. For example, typing in 10m will automatically translate into 1000cm. Very helpful!
- When it comes to scale in level design it’s important to regularly view your objects from the perspective of your player. If you’re making a first-person game for example, there is no point making things feel appropriate from any other perspective but looking through the eyes of your character.
- Playtest. All the time. Especially if you’re making anything in VR. It’s the only way you’ll know for sure if your scale feels correct.
- If you’re looking for help with your approach to scale and proportion within your level blockouts, World of Level design has written up a great primer that puts a lot of what we’ve covered here into practice.
