[funnyflywheel]

This only holds true if you’re flying at or above the transition altitude. The transition altitude depends on where you’re flying: for example, in the USA and Canada it’s 18_000 feet MSL.

[danbtl]

It's still sea-level. The transition altitude just changes the altimeter setting from one that matches the current air pressure to a standard pressure setting.

[funnyflywheel]

I did some more reading, and it turns out I confused QNH with QFE.