Hi,
if it is 40 mm above axle line, you just have to add half of your wheel diameter, right? The latter is strongly affected by your tires.
I have a Suelo Simple frame (with an Odyssey Classic zero offset fork) which has a BB about 40 mm above axle line (roughly measured by myself) which equals 28.7 cm=11.3" above ground with KHE Mac 1 tires.
It is interesting that the frame was described with 11.7" BB hight. I assume this was estimated with 1.9" tires... That is why I think only the measurement above axle line makes sense.