Flush hole size in pan

[shedfooting]

I am thinking of replacing the toilet cistern. At present we have a 40mm flush pipe. Does this men that the pan has a 40mm hole to receive the pipe? I am expecting that new cisterns might come with only 50mm flush pipes.

[Wrongwayfirst]

Deks 40mm Black Rubber Pan Flush/Cone | Bunnings Warehouse (https://www.bunnings.com.au/deks-40mm-black-rubber-pan-flush-cone_p0035049)
flush cone comes in two sizes to suit flush pipes of 40mm and 50mm, the pan is a standard size.

here is the useless information I hold in my grey matter that may or may not shine a light on your job.

40mm is usually a cistern installed at a point above the pan and you can see the flushpipe.
50mm is usually for close coupled toilet suite where the cistern bottom is level with the seat.
there is also an internal version of the 40mm and 50mm flush cone but these are less common and can be replaced with the normal ones in the link.

Old pans had big throats to let the solids out and cisterns had a single flush of approx 12-15 litres usually a 40mm flushpipe.
1990’s pans narrowed the throat and dual flush cisterns were 11/7 litres most common then was 50mm flushpipe.
next iteration of throat change allowed 9/4.5 litres nearly all 50mm flushpipe there was some 50mm tapered to 40mm but not common
current cisterns are 6/3 litres nearly all 50mm flushpipe

you will be able to buy a 50mm flush cone that will fit your pan if your cistern has a 50mm flush pipe.

so the reason for all this potentially useless information is if you have a really old pan that had 12 litres of water sending number two on a trip around the city be wary that a new 6litre flush cistern may only do half the job, which will in fact leave half the job. Number ones will be no issue.
if you currently have a dual flush cistern then you should be ok and have no issues with the pan throat. If you have a single flush cistern mounted high and pre 1990 you might be best to change both, or at least think about the possible repercussions.
cheers