Mayor Bill de Blasio’s first whack at the city budget in the wake of the coronavirus is barely a beginning on what needs doing.

Four months ago, he presented a preliminary $93.5 billion spending plan. Now, despite a loss of perhaps $6 billion in tax income and likely cuts in state aid, his “adjusted” budget is just $1.3 billion smaller. Does he really think he can borrow his way out of this hole?

The mayor’s had it easy on spending until now: A rapidly growing local economy spun off ample tax revenues — and he spent every dime. In his first six years, de Blasio bumped up the budget $20 billion while adding 30,000 heads to the city payroll.

Now his planned “cuts” don’t even equal the spending hikes he’d intended for fiscal year 2021 — when the businesses and other taxpayers that feed city government have been knocked back far more than just a single year.

The Citizens Budget Commission warns that shortfalls in revenue could total $20 billion over the next three fiscal years, but the mayor can’t think about real savings.

He means to nip just $273 million from school spending — at $25 billion, one of the biggest categories in the budget. And even then, much of it is in simple stuff like delaying a pre-K expansion.

He gets another $100 million from programs that are largely dead letters thanks to the lockdowns — for youth summer jobs and Fair Fares outlays for low-income subway riders. More easy stuff.

The city may well get the state’s OK to borrow to help fund operating expenses for a year or two, as it did during past emergencies like the post-9/11 crisis. But new debt and praying for a federal bailout look to be de Blasio’s only “serious” ideas here.

Sorry: You need to look at eliminating entire programs, sir — and talking to the municipal unions about givebacks and layoffs.

Sober up, Mr. Mayor: The days of wine and roses are over. The sooner you start making the hard choices, the smaller the inevitable pain will be.