PCB thickness is the finished Z-dimension of a printed circuit board after the copper, dielectric cores, compressed prepregs and surface finishes are combined. A common nominal rigid-board thickness is 1.6 mm (about 63 mil), but the correct value depends on layer count, copper weight, dielectric build and mechanical requirements. Use the calculator below to estimate a finished stackup; for production, confirm pressed prepreg thickness and tolerance with your PCB fabricator.
Use finished copper weight and compressed prepreg thickness where available. Values are engineering estimates, not a fabrication release.
Important: prepreg thickness after pressing depends on glass style, resin content, copper pattern and lamination conditions. Finished outer copper may also differ from starting foil because of plating. Use your fabricator's approved stackup for production.
This secondary converter targets the common engineering question “how many mm is 1 oz copper?” It is not a full PCB weight calculator.
| Board / layer count | Common nominal targets | Typical reason |
|---|---|---|
| 2-layer rigid PCB | 0.8 / 1.0 / 1.6 mm | General electronics, compact assemblies |
| 4-layer PCB | 1.0 / 1.2 / 1.6 mm | Mainstream multilayer stackups |
| 6-layer PCB | 1.2 / 1.6 / 2.0 mm | More dielectric and plane layers |
| 8-layer PCB | 1.6 / 2.0 / 2.4 mm | Higher layer count, rigidity, impedance structure |
| 10–12 layer PCB | 2.0 / 2.4 / 2.8 mm | Dense high-layer-count designs |
| Backplane / heavy board | 2.4 / 3.2 mm and above | Mechanical stiffness and dense multilayer construction |
These are common nominal design targets, not universal standards or guaranteed fab capabilities. Layer count alone does not determine thickness.
A rigid multilayer PCB is a laminated stack of copper foil, copper-clad cores and prepreg dielectric. The core provides a cured dielectric layer; prepreg is partially cured resin/glass that flows and bonds during lamination. Copper weight contributes additional thickness on every conductor layer, while solder mask adds a small surface contribution.
| Entity | What it is | Thickness relevance |
|---|---|---|
| FR-4 core | Fully cured laminate, usually copper clad | Often the largest single dielectric contribution |
| Prepreg | Resin-impregnated glass used to bond cores/foils | Final pressed thickness varies with construction and resin flow |
| Outer copper | Finished conductor on top and bottom | Starting foil plus plating can affect finished thickness |
| Inner copper | Internal conductor layers | Approx. 35 µm per 1 oz/ft² layer |
| Solder mask | Protective polymer on outer surfaces | Small but relevant when modelling a finished board |
For incoming inspection or a finished-board check, use a calibrated micrometer or thickness gauge at defined flat locations and record the sampling plan. Avoid components, labels, edge bevels and local copper features that can distort the reading. If you need to verify individual dielectric or copper layers, use a prepared microsection / cross-section rather than an external thickness measurement.
The finished PCB thickness does not include the aluminum entry sheet or the HDF/melamine/phenolic backup board used during mechanical drilling. Those consumables increase the total drilling stack height and can affect tool exposure, aspect ratio and process setup, but they are removed after drilling.
For the full drilling stack, use the PCB Stack Height Calculator. For the effect of board thickness on hole geometry, use the PCB Hole Aspect Ratio Calculator.
Aspect ratio is commonly expressed as board thickness ÷ finished or drilled hole diameter. A 1.6 mm board with a 0.20 mm hole has an 8:1 ratio. Higher ratios increase plating and drilling difficulty and should be reviewed with the fabricator, especially for HDI, high-layer-count and reliability-critical boards.
For YUESHAN's drilling-material users, finished board thickness becomes a process input rather than just a mechanical dimension. Thicker boards and larger stack heights increase drill engagement length and can raise the importance of stable entry material, backup support, tool condition and chip evacuation.
1.6 mm (about 63 mil) is the most common nominal rigid-PCB thickness, but it is a convention rather than a universal requirement. Thin, heavy, high-layer-count and connector-driven boards use other targets.
Add the finished thickness of all copper layers, cores, compressed prepregs and optional solder-mask layers. The calculator above separates each contribution so you can see what drives the final number.
Approximately 0.035 mm (35 µm). 0.5 oz is about 0.018 mm, 2 oz about 0.070 mm and 3 oz about 0.105 mm.
Use a calibrated micrometer or thickness gauge on clean, flat finished-board locations. For internal core/prepreg/copper thickness, use a cross-section or the approved fabrication stackup.
No. 1.6 mm is common, but a 4-layer PCB can be thinner or thicker if the core/prepreg build, impedance, stiffness, connector and fabrication requirements support it.
No. Thickness describes the Z-dimension. Board mass additionally requires length, width, dielectric density, copper coverage and often component weight. “Copper weight” in oz/ft² is a separate conductor-thickness convention.
External references provide standards and design context only. Fabrication tolerances and pressed material thicknesses should be confirmed with the board manufacturer.