How To Subtract An Object From Another In Blender

Learning to combine and shape objects is a core skill in 3D modeling. This guide will show you how to subtract an object from another in Blender. It’s a fundamental technique, often called a Boolean difference, that lets you create holes, cut custom shapes, or combine meshes in unique ways.

We’ll cover the simple steps and also explain the common issues you might face. By the end, you’ll be able to confidently use this tool in your own projects. Let’s get started with the basics.

The primary tool for subtracting objects in Blender is the Boolean modifier. Think of it as a digital cookie cutter. You have one object (the dough) and another object (the cutter). The Boolean modifier uses the cutter’s shape to remove a section from the dough.

This process is non-destructive, meaning you can change or remove the effect later. It’s a powerful way to build complex shapes from simpler ones.

What You Need Before You Start

To follow this tutorial, you’ll need a few things ready in your Blender scene.

Two or more mesh objects. For example, a cube and a cylinder.
The object you want to cut from (the Target).
The object you want to use as the cutter (the Tool).
Basic knowledge of moving and selecting objects (G key to grab, right-click to select).

Step-by-Step Subtraction Using the Boolean Modifier

Here is the standard method. It works in almost all versions of Blender and is the recommended approach.

Step 1: Arrange Your Objects

First, place your cutting object inside the object you want to cut. For instance, position a cylinder so it penetrates through a cube. You can see the shape you want to remove.

Step 2: Select the Target Object

Click on the object that will have the hole (e.g., the cube). This is the object that will be modified.

Step 3: Open the Modifier Properties

Look for the wrench icon in the Properties panel on the right. Click it to open the modifier tab.

Step 4: Add a Boolean Modifier

Click “Add Modifier” and choose “Boolean” from the list. A new settings panel will appear.

Step 5: Configure the Boolean Operation

In the Boolean modifier settings, the operation is set to “Difference” by default. This is the subtract function. If it’s not selected, choose it from the dropdown menu.

Step 6: Pick the Cutting Object

Click the eyedropper icon next to the “Object” field. Then, click on your cutting object (e.g., the cylinder) in the 3D viewport. Alternatively, you can click the field and select the cutter’s name from the list.

Step 7: View the Result

The subtraction should happen immediately. You will now see a hole in your target object shaped like the cutter. You can still move the cutter object around to change the position of the hole.

Step 8: Apply the Modifier (If Needed)

While the modifier is active, it’s non-destructive. To make the change permanent and editable as regular mesh, click the “Apply” button. Be sure you’re happy with the result first, as applying can be difficult to undo.

Understanding Boolean Operation Types

The Boolean modifier has three main operations. It’s helpful to know what each one does.

Difference: This is the subtract function. It removes the volume of the second object from the first.
Union: This combines two objects into a single, solid mesh, filling any interior space.
Intersect: This keeps only the volume where the two objects overlap. Everything else is removed.

Common Issues and How to Fix Them

Booleans can sometimes produce strange results, like flickering faces or missing geometry. Here are common problems and their solutions.

Problem 1: Messy Geometry or Artifacts

This is the most frequent issue. It happens because Boolean operations create very complex geometry where the objects meet.

Solution A: Ensure your base meshes are clean. Avoid objects with non-manifold geometry (like inner faces or loose edges).
Solution B: Use the “Solver” option in the modifier. Switch between “Fast” and “Exact” to see which gives a cleaner result. The “Exact” solver is often more reliable.
Solution C: After applying, use the “Merge by Distance” tool (in Edit Mode, press M) to clean up duplicate vertices.

Problem 2: Nothing Seems to Happen

You add the modifier but your object looks unchanged.

Solution: Check that your cutting object is actually intersecting the target. If it’s not touching, there’s nothing to subtract. Also, verify you selected the correct object in the modifier’s object field.

Problem 3: The Modifier is Grayed Out or Missing

You might be trying to add it to the wrong object type.

Solution: Boolean modifiers only work on mesh objects. You cannot use them directly on curves, text, or metaballs without converting them to a mesh first.

Alternative Method: Using the Quick Boolean Tool

Blender also offers a faster, but more permanent, method from the 3D viewport. This is great for quick cuts but offers less control.

Select both objects. Select the cutter object last (it will have the yellow outline).
Press the shortcut Ctrl + – (Control and the minus key).
The subtraction will happen instantly, merging the objects into one mesh.

Be careful with this method, as it applies the boolean immediately. It’s harder to adjust the cut afterward compared to using the modifier.

Best Practices for Clean Boolean Results

Following these tips will save you alot of headache and produce better models.

Use Simple Shapes as Cutters: Complex cutters create complex results. Use cylinders, cubes, or spheres where possible.
Check Normals: In Edit Mode, turn on “Face Orientation” in the Viewport Overlays. Blue faces are outside, red faces are inside. Make sure all faces on both objects are blue. Inverted normals can cause booleans to fail.
Apply Scale: Always select your objects and press Ctrl+A > Apply Scale. Non-uniform scale can distort boolean operations.
Remesh After Applying: For very complex shapes, consider using a Remesh modifier after the Boolean to create a cleaner topology.

Practical Project: Creating a Simple Keychain

Let’s use subtraction in a real example. We’ll make a keychain with a heart-shaped hole.

Add a cube and scale it into a flat rectangle (S, then Z, then 0.1).
Add a heart-shaped curve object (Shift+A > Curve > Heart).
Scale and position the heart so it’s centered on the rectangle.
With the heart selected, go to Object > Convert > Mesh to turn the curve into a mesh.
Select the rectangle (your target), add a Boolean modifier, set to Difference.
Pick the heart mesh as the cutter. You should now see a heart-shaped hole.
For a smooth result, you can add a Bevel modifier after the Boolean.

Going Further: Using the Knife and Bisect Tools

While not strictly boolean, the Knife and Bisect tools in Edit Mode can also subtract geometry in a more manual, controlled way.

Knife Tool (K): Lets you draw a cut line directly on your mesh. You can then delete the unwanted part.
Bisect Tool: In Edit Mode, press N to open the tool panel, find Bisect. This tool cuts the mesh along a straight line defined by clicking and dragging. You can then delete one side of the cut.

These are great for planar cuts or when you need precise control over the cut line.

FAQ: Subtracting Objects in Blender

Can I subtract more than one object at a time?

Yes. You can add multiple Boolean modifiers to a single target object, each with a different cutter. Or, you can join several cutter objects into one mesh (Ctrl+J) and use that as a single cutter.

Why is my model see-through after a Boolean?

This usually indicates inverted normals on the new faces created by the boolean. After applying the modifier, go into Edit Mode, select all (A), and recalculate the normals by pressing Shift+N.

What’s the difference between Boolean and the Knife project tool?

The Boolean modifier works in 3D volume. The Knife Project tool (in Edit Mode, find it in the Mesh menu) projects a shape from the viewport onto your mesh, cutting its outline. It’s a 2D projection, while Boolean is a 3D operation.

Can I animate a Boolean operation?

Absolutely. You can animate the location, rotation, or scale of the cutter object. Since the Boolean modifier updates live, the hole or cut will move and change shape with the animation of the cutter.

How do I fillet or smooth the hard edges left by a Boolean?

Apply the Boolean modifier first. Then, in Edit Mode, you can select the new edge loop and bevel it (Ctrl+B). Alternatively, add a Bevel modifier to the entire object after the Boolean modifier in the stack.

My boolean result is blocky and not smooth. What can I do?

This often happens when using a low-poly object as a cutter on a high-poly target. Increase the subdivision or resolution of your cutter object before the boolean operation for a smoother cut edge.

Conclusion

Subtracting one object from another is a cornerstone technique in Blender. Mastering the Boolean modifier opens up countless possibilities for hard-surface modeling, from mechanical parts to architectural details. Remember to keep your geometry clean and apply transforms for the best results.

Start with simple shapes to practice. Don’t get discouraged if your first few attempts have issues—troubleshooting is part of the learning process. With this guide, you have the knowledge to both perform the operation and fix the common problems that come with it. Now you can efficiently create cutouts and complex forms in your 3D projects.