Why Big Bang Theory star Kaley Cuoco dumped famous ex

The Big Bang Theory's Kaley Cuoco. Photo / AP

Kaley Cuoco has revealed that she once dumped a famous boyfriend because he was "cheap" - and an incredibly bad tipper.

The 32-year-old aired her dirty laundry to Vogue in a new video in which she describes her past relationship with a well-known celebrity who was so cheap he wouldn't leave tips for any servers.

Keeping the real man's name anonymous, the Big Bang Theory star chose to call him John throughout the video to protect his privacy and admitted to dating him when she was just 19-years-old and just starting her career, the Daily Mail reports.

Not only was he a bad tipper to servers at restaurants, drivers or with anyone that would help them while they were out, she said he was just straight cheap.

Once, Kaley even offered to split the bill with him but he was insistent on paying but when the bill finally came he started looking at it seriously while squinting before closing the bill back up without putting a card down or paying.

He then took his phone out and began multiplying an eight per cent tip which is when she said a light-bulb went off and she realized, "Oh my god. He's cheap. He's a bad tipper," she said with shock.

She describes that she grew up with great parents and despite not being rich, her father would always tip people which she learned to do in her own life.

"I knew I had to be with a guy in the future who was the same because I was that way," she says, adding that she thought: "How would I ever introduce this guy to my dad?"

"I can't let my dad who my dad is like my idol, see my cheap boyfriend. That's what it was. My cheap, hot boyfriend and my dad doesn't care if he's hot, my dad cares if he tips. I couldn't ever admit to my dad that that's who this guy was. I wouldn't have been able to live with myself, no matter how hot he was."

At the very end of the video Kaley looks directly into the camera and says, "You would die if I told you who this was. Okay, I'm going to tell you. His name is -" and then the video cuts off.

Cuoco is now engaged to Karl Cook, 26, who is a professional equestrian.