Estimating cable runs when building your home theatre system
The key is planning ahead. If it's rear cables, avoid buying separate runs and making your contractor work with them. Buy a large roll instead, or let your contractor sort it out.
The amount of cable depends on how many speakers you place, the size of your room, and also whether you build in any redundancy..
Eg, one may measure from point to point, that the distance from the front feature wall to the speaker, and determine that it's 5m. But your electrician may run things differently and have to go to the side wall, then upwards and down.
You will also need to have spare amounts at each end to allow for flexibility for placement.
Also is Atmos the last word? Certainly not, there can be new formats, eg Auro is just round the corner, so if you are building something plan for more if you can. Just run the cable and place it into the false ceiling, and cut it out later..
As to what cables one should use, a rule of thumb is to use larger gauge cables. Eg, I used In-wall specced 12 AWG cables, with a thick jacket. For shorter runs you can also use 16 AWG cables, which I am using for a different build.
Remember if you skimp on the cables now, you won't get a chance to change them later.
I have no financial interest or other interests in any of the items / events I write about.