According to <http://referencedesigner.com/cal/cal_02.php>, the conversion between "oz" and "mil" (thickness) for a PCB trace is 1.37. Also, according to `zcalc.exe` (<http://www.fedevel.com/welldoneblog/wp-content/uploads/2011/08/Zcalc.zip>) 4.8mil correspond to 3.5 oz.

Now I get the following table from my foundry:

```
weight (cu)  thickness (mil)
0.25         0.30
0.375        0.45
0.5          0.6
1            1.2
2            2.4
3            3.6
4            4.8

```

These numbers are off by quite a bit.

1. How can this difference be explained?

Now I want to calculate the thicknes of my stripline (e.g. with the calculator referenced above).

2. But which number should I use/trust from the table for my calculations? For example, for 4oz copper ... should I use 4.8mil should I use 4x1.37=5.48mil?

(I would tend to 4.8mil because the input to the stripline equations is thickness but I do not understand the discrepancy)