An easy way to estimate this is:
- measure the width and thickness of your braid. Calipers are good for this so you can get accurate measurements and press the copper strands together into a tight bundle.
- multiply W x T to get the cross-sectional area of the braid
- plug that into an AWG-to-cross-section conversion tool to see where your braid lands compared to common AWG.
Not perfect, but it will get you close enough.