Estimate: 10 trillion gallons drenched California

How much rainfall has hit California in the last 10 days?

Ten trillion gallons, according to Ryan Maue.

That’s enough to fill 15.1 million Olympic-sized swimming pools or power Niagara Falls for 154 days.

Using data from the National Weather Service, Maue -- a Florida-based meteorologist for WeatherBELL Analytics -- calculated that an average of 3.5 inches of water fell across the Golden State.

In places like the Sierras, where several inches of snow fell, Maue’s model liquefied the powder: one inch of water for every 10 inches of snow.

Since one inch of rain in a square mile works out to 17,378,742 gallons, and California has 163,696 square miles -– voila, 10 trillion.

“It’s an accurate number, but it’s based on how good the precipitation data is,” Maue cautioned. “There’s no way to know exactly.”

Craig Shoemaker, a meteorologist with the National Weather Service’s Sacramento station, agreed that it’s a “kind of a neat number” but, alas, imperfect.

“We don’t take instantaneous observations at every point in the state,” Shoemaker said. “There’s going to be some level of inaccuracy.”

Maue’s data was based on totals from 4:00 a.m. Friday -- meaning that daylong rains across Southern California on Friday could push the total up higher.

For breaking news in California, follow @MattHjourno. He can be reached at matt.hamilton@latimes.com.