It would cost the Big Apple nearly $14 billion to bring the estimated 50,000 illegal basement apartments across New York City up to code, The Post has learned.

The tallies were included in a draft report City Hall will submit to the federal government for a $188 million aid package following the devastation of Hurricane Ida.

The storm hit the Big Apple just over a year ago with torrential rains that flooded underground apartments in Queens and overwhelmed sewers across the five boroughs. At least 13 people died.

“This issue is going to continue to impact the city due to the affordability crisis, there’s just no way around it,” said Queens Borough President Donovan Richards. “Climate change is going to end up costing us more than $14 billion. There has to be some city, state and federal intervention here. We’re in a housing crisis.”

It is apparently the first time that City Hall has ever officially put a price tag — $13.7 billion — on what it would cost to bring the tens of thousands of vulnerable homes up to code.

The computations were based on a pilot program launched by then-Mayor Bill de Blasio to legalize underground units in East New York, as an effort by his administration to upgrade the Big Apple’s stock of housing for lower-income households without the pitched battles that come with zoning changes and development of new buildings.

Overall, just six apartments in the outer Brooklyn neighborhood have either been renovated or are under construction, City Hall said late Monday.

Previous city reports on the program touted that “just over 100”  had “completed the detailed home assessment,” though more officials identified 8,000 units that could have potentially qualified.

It cost an estimated $275,000 to $375,000 per apartment to bring them up to code, even after the city eased its own regulations as part of the pilot.

The 2022 draft report for the federal aid states that expanding the effort — would likely be futile without major changes in state law. In it, city officials disclose they plan to spend a small fraction of the hurricane aid allotted — $400,000 — to further study conversions.

“[T]he process of bringing a basement apartment into safe and legal use is too difficult and expensive for many homeowners who could benefit from legally renting out a secondary unit in their home,” officials told the feds.

“Through this effort,” the draft report stated about the pilot program, “it became clear that the City cannot meet its goals for basement conversions without further analysis and statutory changes at the state level.”

The report does not outline what changes officials hope to get from state lawmakers.

But City Hall said in a letter sent to two lawmakers on Friday — Councilwoman Pierina Sanchez (D-The Bronx) and Councilwoman Sandy Nurse (D-Brooklyn) — that the Big Apple would need modifications to state regulations that strictly limit adding new units to existing buildings.

“As we have said for months, what we must do to truly protect New Yorkers is change the rules to legalize and protect basement apartments,” said City Hall spokesman Charles Lutvak, in a statement.

“Mayor Adams’ City of Yes plan [proposed changes to city zoning laws] is part of that effort, and he has also been a leading voice in support of the state legislation we need to make safe, basement apartments a reality,” he added.