V over I X R = amps.
The std fuel pump consumes 13 AMPS at 12 VOLTS, so less than 13 amps as the voltage is usually around 13.5 or so.
Don't got mental on the cable size, don't even think about resistance at this level and length of lead.
I would go for 28/030 FLAT TWIN, so you beef the EARTH at the same time, this will carry 17.5 amps continuous.
If you want I can work out all the resistance values etc, but pointless you do NOT need cable big enough to jump start the QE2, despite what some tuners say.
tabetha