New York City’s childcare system to provide universal coverage for more children would cost about $735 million a year, according to a new report, raising questions about how Mayor Zohran Mamdani would finance a signature proposal.

The study by New Yorkers United for Child Care, an advocacy group, puts a price tag on the cost of extending coverage to full-day, year-round care, including summers, for about 81,500 kids in the 3-K and pre-K category. Those children are currently limited to publicly funded programs that generally follow the traditional school day and school year.

The study estimates that extending care to full days would cost $440 million annually, with another $295 million needed to cover the full year. The expansion would help eliminate what the group calls a “patchwork of care,” in which families rely on babysitters, relatives and summer camps to cover gaps in publicly funded programs.

The estimate for Mamdani’s pledge to expand free childcare across the city highlights the fiscal challenge of making the program universal. The mayor has said the effort would be financed in part through higher taxes on wealthy New Yorkers, while also relying on substantial state support.

In January, Governor Kathy Hochul committed $1.2 billion over two years for New York City’s childcare program, allowing the city to expand the number of 3-K seats it currently offers to make the program universal, and to create a new pilot 2-K program that serves roughly 2,000 two-year-old children in select areas across the city, beginning this fall. The mayor’s office didn’t immediately respond to a request for comment.