About the Oz to Mils Calculator
Use this converter to estimate printed circuit board copper thickness from copper weight in ounces per square foot. It is useful for PCB designers, engineers, students, and buyers who need to compare common copper weights such as 0.5 oz, 1 oz, and 2 oz in mils, inches, millimeters, or microns.
How to use this calculator
- Enter the copper weight in oz/ft².
- Choose the conversion basis: PCB nominal or density-based.
- Read the estimated copper thickness in mils.
- Review the equivalent thickness in inches, millimeters, and microns.
- Use only values of 0 or greater for copper weight.
How it works
The calculator treats the entered value as PCB copper weight in ounces per square foot. It multiplies that weight by the selected conversion factor to estimate thickness in mils.
With the PCB nominal basis, 1 oz/ft² is treated as approximately 1.37 mils. With the density-based basis, 1 oz/ft² is treated as approximately 1.3404 mils.
After finding mils, the calculator converts to other units using 1 mil = 0.001 inch and 1 mil = 0.0254 millimeters. Microns are then found by multiplying millimeters by 1,000.
This is an engineering estimate for copper foil thickness. Actual finished PCB copper thickness can vary due to plating, etching, fabrication process, and manufacturing tolerance.
Example calculation
If the copper weight is 1 oz/ft² and the PCB nominal basis is selected, the thickness is 1 × 1.37 = 1.37 mils. That equals 0.001370 inches, about 0.0348 millimeters, or about 34.8 microns.
Frequently asked questions
What does oz mean for PCB copper?
In this context, oz means ounces per square foot of copper area, not fluid ounces and not a standalone weight measurement.
How thick is 1 oz copper in mils?
Using the common PCB nominal rule, 1 oz copper is about 1.37 mils thick. Using the density-based conversion, it is about 1.3404 mils.
How many microns is 1 oz copper?
With the PCB nominal basis, 1 oz copper is about 34.8 microns. The exact value depends on the conversion basis used.
Why are there two conversion bases?
The PCB nominal value is a common industry rule of thumb, while the density-based value comes from a more direct physical conversion using copper density.
Is finished copper thickness the same as copper weight?
Not always. Finished PCB copper may be thicker or thinner than the starting foil estimate because of plating, etching, and fabrication tolerances.