How do I convert layer count to thickness?

Multiply the number of solid layers by the layer height: thickness = layers × layer height. For example, 5 top layers at a 0.2 mm layer height give 1.0 mm of solid top. The same formula applies to the bottom layers.

How many top and bottom layers should I use?

Aim for about 4–6 solid layers, or roughly 0.8–1.2 mm total, on both top and bottom. With a 0.2 mm layer height that is 4–6 layers; with a 0.1 mm layer height you need more layers to reach the same thickness. Thinner total solid risks gaps and sagging.

What is pillowing and how do I stop it?

Pillowing is the bumpy, sagging or gappy top surface that appears when too few solid top layers bridge over the infill below. The top layers must span the infill gaps and cool before more plastic is added. Adding solid top layers — typically reaching at least 0.8–1.0 mm — and improving part cooling fixes it.

Do top and bottom need the same layer count?

Not necessarily. The bottom prints on the smooth build plate so it often looks good with fewer layers, while the top must bridge over infill and usually benefits from one or two extra solid layers. Many users set the bottom slightly thinner than the top for this reason.

Does layer height change how many solid layers I need?

Yes. The recommendation is by thickness, not count. At 0.2 mm, four layers give 0.8 mm; at 0.1 mm you would need eight layers for the same 0.8 mm. Always think in millimetres of solid skin and convert to a layer count using your chosen layer height.

Top/Bottom Layer Count to Thickness

The solid top and bottom of a 3D print are built from full solid layers that close off the part above and below its hollow infill. Set too few and the top sags into the infill gaps — a defect called pillowing — while too many waste time and plastic. This calculator converts your top and bottom layer counts into actual thickness in millimetres, and works backwards to tell you how many layers reach a target thickness.

How it works

Each solid layer is exactly one layer-height tall, so the total solid thickness is the layer count times the layer height:

top thickness = top layers × layer height

bottom thickness = bottom layers × layer height

To hit a specific target thickness you round up, since you can only print whole layers:

layers needed = ceil(target thickness / layer height)

The recommended minimum is roughly 0.8 mm, or about 4 layers at a 0.2 mm layer height. The calculator flags top or bottom counts that fall short of that guideline.

Example

Five top layers at a 0.2 mm layer height:

top thickness = 5 × 0.2 mm = 1.0 mm

To instead guarantee a 1.0 mm solid skin at a finer 0.1 mm layer height you would need ceil(1.0 / 0.1) = 10 layers — twice as many for the same thickness, because each layer is half as tall.

Notes

Always reason in millimetres of solid skin, not raw layer count, because the right count depends entirely on your layer height. The top layers have the harder job: they must bridge across the infill voids and stay flat as they cool, so they tend to need a layer or two more than the bottom, which prints flat against the build plate. If the top of your prints looks bumpy or shows the infill pattern, add solid top layers until you reach at least 0.8–1.0 mm and improve part cooling. All calculations run locally in your browser.