.....Divide that number by number of miles per kWh and add about 10% for energy conversion losses. ...
That's actually a false truth, if you get my drift.
Almost 50% of our electricity comes from burning gas, and a gas fired power station produces around 550g(eq)CO2/kWh. Any marginal demand increase comes from gas, so if you plug in your EV and all the renewables and nuclear are already being used (which they will be), then it will be charged by a gas power station at 550g/kWh (plus losses, let's say 600g/kWh).
A typical EV does 4mls/kWh, so that's 150g CO2/mile if powered by a gas station (or about 95g/km to make it easy to compare to ICE cars). A similar petrol car might be around 120g/km real world, ballpark 50mpg.
This is also the false truth about domestic gas boilers. Any marginal electricity produced by a gas power station used to heat your water will result in about twice the CO2 of a domestic A rated boiler. If we can get rid of all the gas power stations then we can start phasing out domestic boilers, but until then it's folly. Even an air sourced heat pump with a typical COP will only do just a little better than a domestic boiler for CO2, but will still cost you more to run (domestic electricity typically 4x gas per kWh).