KM/H to MPH (Japanese Car)

If your car has no way in the settings to convert to MPH from KPH you can use this mental trick: 8 KPH = 5 MPH. So 80 kph is 50 mph, 40 is 25, 120 is 75. It isn't exact, but it is so close as to not matter.
Make up a cheat sheet and stick it on the dash for the speeds you need.

 

In North America, early year 4th gens (2016 included) had no way of switching from the default speedometer display: mph displays could not be switched to kmh, and vice versa. Toyota never fixed it for the early years, maybe offered some sorta conversion decal?

 

I did not know that. Mine was a dealer demo and has fuel use record going back to 10/2015. My memory - such that it is - wants to say I can change mine but I have no real confidence in that, will check it out. I seem to be an outlier in many ways.
The OP is talking about a Japanese market 2017 model, though.

 

My 2017 Prime has a setting to switch from km/h to mph. I wish there was also a setting to bump up that ridiculous NA 10 kWh/100 km to 40 kWh/100 km that Europe has. It's always pegged to the top when in EV mode.