Parts ending up a few decimal places out of the specified size with a ~18mm

I make a model and use only exact mm figures with no decimals.
then i send to opencutlist and it shows me that my component is bigger or smaller than the size i input and i end up with a shelf for example that is ~18mm thick, i then check and its shows the part is 17.98mm or 18.25 mm for example.

its really bugging me.

tried making the precision in my units to 0.0 and 0 but not avail.
really dont want to have to go through and manually correct hundreds of components.

any ideas whats going on?
model attached for reference.
nancy living room.skp (1.1 MB)

Without looking at the model, my first suggestion would be to turn off Length Snapping (Window menu>Model Info>Units.

Some of your components are drawn off axis

You can see the bounding box doesn’t align with the shelf

Also, there is something weird going on with axis in general. I feel like I’ve missed something

This is the wrong way to get things accurate, the Display Precision is just that Display. It means it will round things up or down rather than show you exact sizes. Setting the Precision to the finest option will show you inaccuracies as you go so you can fix them.


To add to the above - the length snapping option is the one that you want to set if you don’t ever want to be able to use a tool to go under a certain threshold.

If you want pushpull or whatever to work with 1mm steps, set length snapping to that.
If you need to use smaller increments you can still type them in.

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Changing Display Precision doesn’t affect the accuracy of your models. It only affects how precisely dimensions are shown. That’s why it’s called Display Precision. I find the best practice during modeling is to set Display Precision as high as it will go. That way I can see that dimensions might not be what I want them to be and I can fix them before they create problems.

The thing @Anssi about turning off Length Snapping is important. Besides making it easier to create components with incorrect dimensions, it results in placement errors. For example, on the case at the left in your model, there is a small gap between the top and that component you called ‘toptop’ and the ‘toptop’ component is positioned slightly below the top face of the case side. If you use those parts of the model as references for modeling additional parts, those parts are going to wind up with bad dimensions.

This is a thing where a little sloppiness in the beginning just multiplies as you continue modeling.

Maybe you can just round the numbers and everything will work out. Personally I don’t like the idea of doing that and I would go through the model with a fine-toothed comb after seeing the cutlist to fix things. And the next model would be made with precision from the beginning. It is definitely doable to make a precise model.

ETA: I meant to add that you can reduce Display Prcision later if you are going to use SketchUp’s Dimension Tool although if you are using LayOut to create shop drawings you can just set LayOut’s Dimension Tool to the desired precision.


That is the original idea of it, a sort of pseudo grid, but the reality of it is that it can cause forced errors and is anecdotally responsible for innumerable slightly twisted models. Because it forces a specific length it can snap just off the expected snap point rather than follow the inference system. Once one point is wrong it will propagate through the whole model. Best advise is not to use it.


I guess if you are doing it for very small increments it’s easy to slip still?
Not so much of a problem if you are snapping to whole feet or meters

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Yes, not a problem if you’re building with a JCB and a chainsaw.

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I’ve found my error rate (imprecision), goes way down when I model with color by axis. I have scene tabs to toggle quickly between modeling view and material preview.

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Color by axis is not a sure thing, it by itself can introduce small errors.

You can eliminate more of the errors by using the inferencing that is provided. The arrow keys are a must in the workflow. Check out Inferencing and More inferencing on the YouTube channel.


Agree on using arrow keys, I also use lots of guides. But how does using a visual style introduce small errors?

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Color by Axis doesn’t induce errors but it doesn’t always show very slight misalignments. Depending on it for the precision of your modeling isn’t a good idea.

Here’s an example. The top edges aren’t off by much compared to the bottom edges but they should be identical. This isn’t a lot of error, especially in terms of woodworking or architectural modeling but this sort of error can multiply if it’s not caught early and fixed.


thanks everyone! much learning for me in there :slight_smile: ill be sure take note of those tips and adjustments.
seems to only happen on certain models some of the time and seems to come in waves.
this was definitely one of my lazier models as its for my house not a client XD normally a bit more profesh when it come to tags and scenes etc but this has been an annoying pitfall.

Maybe a good lesson. Stay on top of your models no matter who they’re for. The little bit of extra care and effort up front will save you a ton off work later on.

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always does!! when i first started i didnt use groups or components to draw cabinets and boy was it soooo much work. haha

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yea that component seems to have been pushed off axis by a percent of a degree somehow, its weird as i just draw rectangles on axes and then push pull to thickness so im not sure how that happened. just deleted and tried again and no issue!