The figure is contained in a report to be released Wednesday.
The report shows a rapid rise in homeless children and families since the spring when the city eliminated a rent subsidy program.
The Wall Street Journal (http://on.wsj.com/sWXCDP ) obtained an advance copy of the report by the advocacy group Coalition for the Homeless.
The report shows that since May, children in shelters rose 10 percent and homeless families went up more than five percent.
The mayor's office on Tuesday defended its approach to homeless but acknowledged it needs continued attention.
The City Council is set to hold a hearing Wednesday on a new shelter-eligibility policy for single adults.