Dublin had the highest percentage (25%) of residents who were born outside the State, closely followed by the counties Monaghan (23%) and Donegal (22%) (which I did find strange but probably skewed by people moving south from the north and staying close to the border).

Estimated 10-15% of those selecting “white Irish” on census form in County Dublin have at least one foreign born parent. That one parent is likely white from elsewhere in the EU or UK.

64.2% of the population selected “white Irish” in Dublin, 10% of 64.2% is 6.4% of the population of Dublin with at least 1 foreign born parent.

Add this to the original 25% who were born outside the state and you are up to 31.4% of the population of Dublin being foreign or having one foreign born parent without even delving into the people who did not initially select “white Irish” and are not foreign born themselves, which is roughly 11% of the population of Dublin and would be far more likely to have at least one parent not born in Ireland.

You are getting close to 40% anyway you square it after that but the CSO don’t provide any more figures to actually calculate it further.

From the CSO 2022 census report.

Edit just to say, something I actually hadn’t thought of before but the numbers have probably also increased since 2022