https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp?INT_ID=IB12809#type

My legs for stumps for someone 178cm tall are…
(Cycling, not trouser) inseam 83cm
Thigh 54.5cm
Lower leg 55.5cm

Fit guide says BB-saddle height road bike 80.3-84cm depending upon Eddy/competitive/French fit and 77.5cm for XC mountain bike.

83cm inseam at other websites suggests 90cm pedal-saddle, so ~75cm BB-saddle.

Fit guide talking testicles?

there are many formulas and theories for working out saddle height (and other bike measurements) it’s not set in stone, people usually believe the one they’ve spent most money on

0.883 x inseam is a reasonable guide. Will change if you move saddle forward or back. Your prediction looks high to me. That’s BB to top of saddle. I’m same height and absolutely average size (by bike fit). I ride 74 cm for reference.