I just bought to Hashimoto HMU-7 SU transformers to use with a newly diamond re-tipped AQ 7000 which has one of the lowest coil resistances at 2 ohms.
99% of my LOMC cartridges are about 2 Ohms too.
This is one of my SUTs: Luxman toroidal silver SUT
I can swap the SUT
in the base, as you can see there is a recommendation for use a cartridge with certain coil impedance (under 3 Ohm is one SUT, there is another for about 40 ohms).
So it's not necessary to count 1:10 , 1:15, 1:30 or whatever ... just looks at the recommended connection impedance printed on the SUT input and choose the SUT for your cartridge self impedance accordingly