Whether you’re checking out a beautiful woman or glancing at the new guy at work, count to three in your head and then look away.

Why? Because new research from the U.K. shows that the perfect amount of time to stare at someone is about 3.3 seconds. Any longer or shorter and you’ll creep them out, the study suggests.

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In the study, almost 500 people sat close to a screen displaying different clips of actors staring at them. On average, participants reported feeling uncomfortable when the actor’s gaze exceeded or stopped short of 3.3 seconds.

This isn’t a physiological response, but rather, an unwritten social norm. “People learn and conform to a social standard that establishes how long the mutual gaze should last,” says Nicola Binetti, Ph.D., of University College London.

Humans decided that around 3 seconds seemed like the right amount of time to stare and ran with it, much like we inherently know how firm our grasp should be when giving a handshake, Binetti says.

Related: 7 Things You Didn’t Know About Your Handshake

But say you really like what you see, and you want to keep subtly staring without getting slapped.

In that case, position yourself diagonally from the recipient of your stares, says body language expert Marc Salem, the author of The Six Keys to Unlock and Empower Your Mind. People interpret side glances as less invasive than straight-on stares, he says.

And when you’re talking to someone, keep your eyes on the bridge of their nose, says Salem. This will seem less intrusive than if you were to stare right into their eyes.

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