SolidWorks is an incredibly powerful CAD program that allows to create very detailed parts and assemblies but no matter how complex your model is it’s highly likely that it will use some kind of units system.
American users are generally more likely to work in Imperial units (technically known as ‘United States customary units’) such as inches, feet, pounds and ounces, whereas the rest of the world tends to use the Metric system – millimetres, metres, kilograms and grams.
Luckily SolidWorks makes it very easily to change these units whilst modelling, and even allows you to use a combination of both.
How to tell which unit system you’re using in SolidWorks
As soon as you start any SolidWorks document – whether it’s a part, assembly or drawing – you can instantly check your units system by looking to the bottom right of the screen. You should see a collection of letters that indicates which units you’re currently using. This is likely to be either MMGS – millimetres, grams, seconds, or IPS – inches, pounds, seconds.
How to change units in SolidWorks
You can change the unit type at any time by simply clicking on the abbreviation and selecting your preferred system. Any existing units in the model will automatically be converted into the new units, but the actual dimensions themselves will be unchanged. For instance a length that is set to 1 inch will be converted to 25.4mm – a different number but physically exactly the same distance!
You can click ‘Edit document units to access more unusual unit types, if needed.
Mixing and Matching Units in SolidWorks
One brilliant feature of SolidWorks is that you can use any unit type on the fly, even if your document isn’t set to that unit type. For instance if you’re working in Imperial you can use the Smart Dimension Tool to set dimensions in millimetres just by typing “mm” after the number value. This will then be converted to the equivalent length in inches. So you could input, 10, followed by “mm” and this will automatically change to 0.393 inches.
Similarly, you can do the same if working in Metric simply by adding “in” (for inches) or ” (the symbol for inches) after your number.
Within your own unit system you can also use larger unit types. For example when working in inches, typing “1ft” will automatically convert to 12inches – or one foot. When using metric it’s possible to use Centimetres or Metres (cm or m) and these will convert down to millimetres.
It’s even possible to mix units – so typing, “1 ft 3cm” will convert to 334.8mm or 13.18 inches!
Using Fractions in SolidWorks
As well as writing whole numbers you can also input fractions. Simply type the fraction using the forward slash key. For example for a half type ’1/2’, for a third type ’1/3’ and so on. The fractions will then be converted directly into decimal, so 1/2 becomes 0.5 and 1/4 becomes 0.25.
This trick can be especially helpful for Metric engineers who aren’t used to fractions of inches. Just by inputting ’7/16IN’ the rather cryptic Imperial amount converts to a much more understandable 0.44” or 11.11mm.
Using mathematical symbols to change dimensions
Another great feature of Smart Dimensions is that you can use mathematical symbols to change your dimensions. This may sound complicated but it can really simplify your work and save lots of time.
Imagine you have a bar that is 37.5mm and you need to make it three times larger. Instead of grabbing a calculator you can simply type, 37.5 * 3 and SolidWorks will work out the correct number for you. Other symbols such as plus, minus and divide (+ – /) can also be used, or a mixture of these.
This can allow you to easily make complex mathematical changes quickly and with confidence, and without leaving SolidWorks.
Linking Units in SolidWorks
Finally dimensions can also be linked to other units within sketches. For example – if we require a rectangle that is always twice as high as it is long we can connect these two values. First set one value – such as the length. The second value can then be linked to the first one by typing ‘=’ into the Smart Dimension value, then clicking on the first unit.
We can now follow this linked unit by ‘*2’ to give a new dimension that is always double the length of the first one – even if the first unit changes. Using this method you can create complex sketches that automatically update once a base value is changed, saving lots of time, and avoiding any potential adjustment errors.
Top Tips for working with SolidWorks units
- Set your unit type by clicking on the abbreviation in the bottom-right of the screen
- MMGS for metric, and IPS for Imperial/American are the two most common systems
- Change units on the fly by writing their symbol or abbreviation after the number value
- mm – millimetre, cm – centimetre, m – metre, in or ” – inch, ft – feet
- Fractions can be converted to decimals by inputting them using the / key
- Maths symbols like + – * and / can be used to modify units
- Units can be linked to other values by prefixing them with the = symbol.
Happy modelling!
About the Author: This is a guest post by Johno Ellison, a design engineer with over fifteen years or experience, who specializes in SolidWorks 3D CAD modeling. Johno is the author of the following online SolidWorks courses:
Master Solidworks 2019 – 3D CAD using real-world examples
Master Solidworks 2018 – 3D CAD using real-world examples
Master Solidworks 2015 – 3D CAD using real-world examples
