Ladies saddle.....

[Cycleops]

A DIY way to do it is to place tinfoil on a carpeted step, sit on it and lean forward a bit. Then measure between the indents.

Just don't let anyone see you doing it!

 

[Julia9054]

Just don't let anyone see you doing it!

Definitely less embarrassing than having your arse measured by ex pupils though!

 

[Globalti]

I don't buy into this measuring sitbones story, I think it's a gimmick. I'm slim of hip yet if I measured my sit-bones I'd be buying a saddle off a 1930s tractor.

 

[vickster]

Whereas I find any saddle without a cut out very uncomfortable over about 15 miles.
Also, one might assume that if your backside is big, you will have wide sitbones but width of sit bones doesn't really equate with size of backside which is why it is important to get measured.
A DIY way to do it is to place tinfoil on a carpeted step, sit on it and lean forward a bit. Then measure between the indents. My local Specialized shop has a more technical thing for measuring sitbone width but as I used to teach a couple of the blokes that work there, I wasn't really up for that!

And make sure you do it while wearing your cycling shorts if you wear them