Inputs
- Length in mm
- Copper weight in oz
FPC / PCB Engineering Calculator
PCB Unit Converter: mm, mil, inch, um and oz Copper
Convert PCB and FPC units including mm, mil, inch, um and 1 oz copper to um for drawings, stack-ups and DFM checks.
How to use the Engineering Unit Converter
Engineering unit conversion is a daily PCB and FPC task. Drawings, customer specifications and factory replies often mix mm, mil, inch, micron and copper weight, including quick 1 oz to um conversion.
Common engineering conversions
Formula: 1 inch = 25.4 mm, 1 mil = 0.001 inch, 1 oz copper = 34.79 um
- mm: millimeter.
- mil: one thousandth of an inch.
- oz copper: copper weight per square foot converted to nominal thickness.
Formula Basis
- Formula basis: SI length definitions, inch-to-millimeter conversion and common PCB copper-weight conversion; 1 oz copper is shown as about 34.79 um.
- Engineering note: copper oz values are nominal; use measured finished copper when tolerance matters.
Example
1 mm equals about 39.37 mil, and 1 oz copper equals about 34.79 um.
Outputs
- mil
- inch
- um
- copper thickness
Engineering Notes
- Always confirm whether mil means thousandth of an inch, not millimeter.
- Copper oz is a weight-based convention, often rounded to 35 um for quick communication.
- Use consistent units before comparing factory DFM limits.
Validation Checks
- Drawing unit review
- Stack-up conversion
- Copper thickness conversion
- Tolerance communication
Related Manufacturing Process
- Material Selection - PI / PET / FR-4 thickness, RA or ED copper, adhesive type, coverlay thickness
- Stack-up Design - Total thickness, dielectric spacing, symmetry, controlled impedance
Related Calculators
- Copper Thickness Converter (1 oz to um) - Convert copper weight and thickness, including 1 oz to um, for stack-up and plating reviews.
- Stack-up Thickness & Feature Drawing Tool - Build stack-up thickness and draw coverlay openings, air gaps, through holes, buried vias and blind vias for engineering review.
- Stiffener / ZIF Thickness Calculator - Check assembled FPC stiffener thickness against a connector or ZIF target thickness.
FAQ
Is mil the same as mm?
No. In PCB/FPC engineering, mil usually means 0.001 inch, which is 0.0254 mm.
Why include copper oz here?
Copper weight is one of the most common unit conversions in stack-up and current calculations.