Whatever you think of Tom Cruise, you know he’s not a 6-foot-5, 200-something pound guy, which is the way author Lee Child describes his crime-solving/ justice-dispensing ex-military policeman, Jack Reacher.

But even if Cruise isn’t as physically imposing as the character, he can still bring the intimidation, as he proves in “Jack Reacher.” Cruise carries off the part with a bruising panache, as at home in a brawl or car chase as he is in droll banter with the mere mortals who surround him.

Based on Child’s novel “One Shot,” it’s about a sniper from the Iraq war accused of mowing down a crowd of people in Pittsburgh. Reacher, as is his way, just shows up, “summoned” because of a connection with this sniper who snapped, first in Iraq and now, apparently, in Pittsburgh.

The district attorney (Richard Jenkins) figures it’s an open-and-shut case. His attorney daughter (Rosamund Pike) defends the shooter with the thin hope she can keep him out of the electric chair.

Reacher, a “Who IS this guy?” veteran and drifter living off the grid, offers not to help, but to “bury this guy.”

Cruise plays Reacher as quiet, unhurried and observant. The cops want to know what makes an MP such a serious sleuth, such a careful man around violent men. In the Army, Reacher growls, “every suspect was a trained killer.”

A trashy young woman hits on him in a bar, earning a “cheapest woman tends to be the one you can’t afford” lecture from Reacher. Her brutish brothers take offense.

“Is she a good kisser?” Reacher quips.

An auto parts clerk resists cooperating. “I need to see some ID. I need to see SOMEthing,” he says.

“How about the inside of an ambulance?”

The “grassy knoll” cracks by one and all point us, early on, to signs of a conspiracy. And a mysterious, monstrous, one-eyed fiend played by the German director Werner Herzog (“Rescue Dawn”) is up to something, having Reacher followed.

“Usual Suspects” writer turned writer-director Christopher McQuarrie plays up the banter in between the beat-downs. Because you know there’ll be beat-downs. And he preserves Reacher’s personal sense of justice.

The ex-soldier demands that the lawyer meet the families of the victims, and she does, treating herself and us to poignant portraits of innocent people gunned down, seemingly at random, a lovely grace note for a violent action picture to have.

McQuarrie doesn’t reconstruct the actual crime in enough ways to make crystal clear what actually happened. And when he errs, he errs on the side of silly, going for laughs, bringing in Robert Duvall for a Cruise-Duvall “Days of Thunder” reunion that’s comical pandering.

But Cruise’s gift as an action hero is that he believes these tough-guy lines, or makes us believe them. When he twists a bad-guy’s fingers, he says, “Look at your friends (already beaten up). Look at my face. Do you EVER want to see me again?” We buy it.

You don’t need to be a giant, physically imposing man to manage that.