[Blender→Unity] Colliders Become Huge After Importing an FBX: Cause and Fix

Published: September 20, 2026
For: Anyone who imported an FBX from Blender into Unity and found colliders or child objects unexpectedly huge

The problem

You export a model from Blender and import it into Unity, and the Armature's Scale is 100. The model itself looks the right size, but a collider attached to a bone ends up 100 times larger.

Clicks and raycasts start hitting places that have nothing to do with the model.

Cause (in short)

The Scale inside the FBX was 100, so a collider added in Unity became 100 times larger than intended.

Cause (in detail)

With Blender's default export, the FBX declares "1 unit = 1 cm", while the vertex coordinates are written as "1 unit = 1 m" numbers. To bridge that 100x gap, Blender puts a scale of 100 into the Transform inside the FBX.

Unity, for its part, follows the "1 unit = 1 cm" declaration and imports the mesh and bone coordinates scaled by 0.01 (the import settings show "1cm (File) to 0.01m (Unity)"). That 0.01 and Blender's 100 cancel each other out, so the model ends up the right size.

The 100 stays in the Transform, though, so colliders and child objects you add later become 100 times larger — which is how the giant collider happens.

Fix

• In Blender, apply the scale with Ctrl+A → Scale first, then set Apply Scalings to FBX All in the FBX export
• After importing into Unity, check that the import settings show "1m (File) to 1m (Unity)" next to Convert Units

Environment

Item	Version
Blender	5.0.1 (English UI)
Unity	6000.0.58f2 (Unity 6, English UI)
Test model	1.8 m tall cylinder + 3 bones (Bone0-2) skinned with automatic weights

Fix in detail: exporting with Scale 1

The steps below show, on the actual screens, how to export an FBX that comes into Unity with Scale 1. After that, you will find the steps to reproduce the problem.

Step 1: Check that the object scale is 1

Select the armature (and the mesh), then open Object Properties (the orange square) in the icon column on the left of the Properties editor at the bottom right. If Scale under Transform is anything other than 1.000 (such as 0.010), apply it in Step 2.

Step 2: Apply the scale with Ctrl+A → Scale

First select both the armature and the mesh in the Outliner (with only one selected, the scale is applied only to that one).

Then move the mouse over the 3D Viewport, press Ctrl+A and choose Scale in the Apply menu. The scale becomes 1.000 and the model keeps its size. If the scale was already 1 in Step 1, you can skip this step.

Step 3: Open File → Export → FBX

From the File menu at the top left, hover over Export and choose FBX (.fbx).

Step 4: Set Apply Scalings to FBX All

On the right side of the export window, Apply Scalings in the Transform panel is set to All Local by default. Open the drop-down and choose FBX All.

FBX Units Scale gave the same result in our tests.

Step 5: Click Export FBX

Enter a file name at the bottom and click Export FBX at the bottom right.

Check 1: Unity's import settings show "1m (File) to 1m (Unity)"

Put the exported FBX in Unity's Project window and click it to select it.

Selecting it brings up the Model tab in the Inspector. If it says "1m (File) to 1m (Unity)" next to Convert Units, no unit conversion is happening.

Check 2: The Armature's Scale is 1

Place the FBX in the scene and select Armature. If the Transform scale is 1, you are done.

A radius-0.3 Sphere Collider attached under a bone now stays at the intended 30 cm radius.

Reference: exporting from a script

In a script, Step 2 is transform_apply and Step 4 is apply_scale_options.

import bpy

armature = bpy.data.objects["Armature"]
body = bpy.data.objects["Body"]

bpy.ops.object.select_all(action='DESELECT')
armature.select_set(True)
body.select_set(True)
bpy.context.view_layer.objects.active = armature
bpy.ops.object.transform_apply(location=False, rotation=False, scale=True)  # Step 2

bpy.ops.export_scene.fbx(                     # Steps 3-5
    filepath="model.fbx",
    use_selection=True,
    apply_scale_options='FBX_SCALE_ALL',      # Step 4: Apply Scalings = FBX All
)

How to reproduce the problem

The steps below reproduce the problem.

Reproduce 1: Export with Apply Scalings left at All Local

Open File → Export → FBX and export without changing Apply Scalings from All Local.

Reproduce 2: Import into Unity and select the Armature

Place the FBX in a Unity scene and select Armature. The Transform scale is 100 on X, Y and Z. The model still looks 1.8 m tall, not huge.

Reproduce 3: Attach a collider under a bone

Add a Sphere Collider as a child of Bone1 and set its radius to 0.3 (meant to be 30 cm).

In the Scene view, the collider is a sphere with a 30 m radius. The model itself is a small dot at the center.

Summary

• Scale becomes 100 because the default export writes the FBX in centimeters, and Unity's 0.01x is canceled out by a 100x on the objects
• The model looks the right size, but colliders and child objects under the bones become 100 times larger
• Apply the scale with Ctrl+A and export with Apply Scalings: FBX All to get Scale 1 in Unity
• After importing, check that the import settings say "1m (File) to 1m (Unity)". Keep Convert Units on

Missing bones are a separate problem with a different cause and fix. See [Blender→Unity] Bones Missing After FBX Export: Cause and Fix.

Models built with this pipeline run in PoseMirror, a free tool that turns a photo into a 3D pose.