It costs a big pile, $1.8 million an inch, to clear snow from city streets, according to a report released Wednesday.

Using the new measure — nearly twice the $1 million-an-inch figure city officials have used for years — this week’s snowfall will cost taxpayers about $18 million, said auditors for Comptroller Scott Stringer.

One surprise in the report: “Costs per inch of snow removal are significantly higher in light snow years than in heavier ones,” the auditors said, citing fixed city costs such as equipment and manpower.