When you layout your PCB, one of the basic decisions to take is the trace width. I have come across various online tools which can be used for calculating trace width, but most of them were either obsolete or unreliable. I recently found a very comprehensive tool for all PCB design calculation needs.
You can download the Saturn PCB Toolkit for free from here. I use the tool mostly for calculating trace widths based on the current handling capability required, impedance characteristics of the trace, via properties, etc. The tool also has various other calculations which may be of use. The website also has an informative help page.
Now you can use your brain for things that are more challenging – like understanding the Duckworth–Lewis method.