Correct Pipe for Toilet Waste That runs Under Floor

[carbar]

Hello

I am installing a new toilet which will involve running the waste pipe under the floor of the adjoining room. The distance between the wall that the toilet will be attached to and the outside of the wall where it will join the existing vent pipe is approximately 2.8m.

Would a 3m pipe be long enough or would I be better getting a 4m pipe? Would this https://www.bes.co.uk/110-mm-x-4-m-plain-end-pipe-black-12514 be appropriate (I want a single complete pipe, rather than have joint under the floor)?

Thanks,

Carl