How to scale model to real units?

Hello everyone.

I modeled a gun with reference image. But the image not match real size.

How i can scale the model properly to the real size.

I know only lenght.

Length: 820 mm

Barrel length: 200 mm

What i do need now scale separately? And how to do it if i know only lenght?


Here is my barrel for example. (real size is 200 mm)

Maybe try setting the one known dimension in the Dimensions field. (I’m assuming its the x dimension)
Blender will adjust the corresponding scale factor. Then just copy the scale factor to the y and z scale, as well.

If you made all parts of your model at the same scale jou should be able to use the same scale factor for all parts of the model.

If that gives you the desired result, you can just apply the scale (ctrl+A > Scale) to set the scale factor to 1 while keeping the dimension the same.

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I tried it but if i scale the X on 20 cm is scaled only on X. Where are the other scale factor of Y and Z which i need to copy to Y and Z?
Thank you many times for help me : )

Yes, changing the x-dimension will only scale the object in the x-axis. Follow the next steps and you should get the desired result.
I made some annotations to your screenshot to hopefully make things more clear :slight_smile:


Something to note for step 2: Considering the scale already is so small, you might not see the displayed value for the x-scale changing as it is rounded to only show 3 decimal places.
The value is still adjusted. Just double-click it and it should display the complete value.

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Yeah, I’d apply scale first then follow those steps and apply the scale again as a last step at the end.

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Just hit ‘S’ and start scaling the entire model while keeping an eye on the dimension of the axis you know. If the barrel length is along X axis for example, just scale the model uniformly until the X value reaches the desired dimension you have.

I do this all the time to scale objects like 3D humans. Since we know the Z dimension of a human is somewhere around 1.8 m, I scale the model uniformly until the Z dimension reaches 1.8 (by the way using Shift to slow down scaling when needed). This will be accurate enough. May be a few millimeters off but nobody can notice it.

Just a small heads up though. Be sure to apply the rotation before doing this, otherwise you might end up looking at the wrong axis when the rotations are messed up. And also when you have multiple objects in your model, make sure to have the appropriate object as active before scaling.

Since you modeled the gun from reference images, the proportions will be in place, so you can scale everything together unformly without having to deal seperately with each axis.