Adhesive bed thickness?

[TimmoF]

On a liquid screed (which is flat) what depth adhesive bed can/should I use?
I'm trying to establish how much adhesive I need to buy and just for clarity, I mean the actual finish bed depth not the trowel size to use.
They're limestone tiles 15mm thick.

Many thanks!

 

[Hobnob]

I usually reckon on a max of 3sqm per 20kg bag.
This takes into account the back skimming of every tile but if there is a need for some bedding out then extra units will be required.

 

[TimmoF]

Many thanks Hobnob, Cheers