Lenny Kravitz reveals the simple test he uses to know if he's still fit at 62

Lenny Kravitz may be one of rock's fittest stars, but he says he doesn't need an expensive fitness tracker to stay in shape.

Instead, the Grammy winner relies on one brutally honest test that's never failed him — whether he can still squeeze into a pair of 28-inch-waist pants.

Kravitz, who's known for his shirtless performances and sculpted physique, revealed that his waist size remains the ultimate indicator of his health — and it came from a fellow Hollywood heavyweight.

LENNY KRAVITZ WAS ‘NERVOUS’ WHAT MOM WOULD THINK FIRST TIME HE WORE WOMEN'S CLOTHES

Lenny Kravitz credits Mick Jagger for inspiring his training and nutrition regimen.  (Jonny Marlow / Men’s Health)

"I can gauge everything by how I’m in my pants," he said. "Like, if my pants are a little tight, I know I’m getting outta’ shape. My friend Denzel Washington gave me this phrase, ‘The pants don’t lie, the pants don’t lie,’" he said in a cover interview for "Men's Health."

Kravitz said his workout wardrobe also serves a practical purpose. The singer, known for performing in leather pants and denim, often trains in the same clothes he wears onstage.

"I perform onstage in leather, denim, whatever, so those are the pants I wear to train," he added. "It also means I can fit in a workout anytime, anywhere."

While Kravitz has built a sculpted physique, the 62-year-old admitted there's still one area he'd like to improve.

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The 62-year-old rocker said he stays fit naturally without fitness trackers or peptides. (Jonny Marlow / Men’s Health)

"Not right now, and I don’t mean that to sound like I’m into myself, but I’ve put in the work and I feel really good. But I gotta fill out my legs a little bit."

His trainer has since increased lunges and deadlifts, even borrowing a page from Arnold Schwarzenegger's legendary bodybuilding approach of exposing his calves to keep himself focused on improving them.

Kravitz also spends little time resting between exercises.

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Instead, he powers through hundreds of abdominal repetitions each workout, helping maintain the 10-pack that's become one of his signature features.

The musician acknowledged that his highly defined abs have sparked online speculation, with some questioning whether his physique is natural. Kravitz pushed back on those assumptions.

Lenny Kravitz appears on the cover of Men's Health magazine. (Jonny Marlow / Men’s Health)

"All this is natural: no peptides, no human growth hormone, no testosterone," he said, adding, "There’s nothing wrong if people want to do those things. But there’s an alternative. You can do it naturally with exercise and food. Is it harder? Yes. Does it take more work? Yes. But that’s how I choose to do it, and it’s 100 percent attainable."

The musician said his commitment to fitness wasn't always part of his routine. Despite decades in rock and roll, Kravitz said he didn't begin training seriously until the mid-1990s.

One music legend changed his perspective.

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Lenny Kravitz trains in leather pants, does hundreds of abs reps and relies on one old-school waist size test. (Ralph Bavaro / NBC)

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"The mid 90s is when I really began training, although I was already very health conscious, but I hadn’t put the two together yet," he said. 

"Most people I knew in the rock and roll world were not taking care of themselves in that way but Mick Jagger was a big influence on me. We were on holiday together once in the Bahamas and I watched how disciplined he was about his training and nutrition and realized that this was a major part of his formula."

More than 30 years later, Kravitz said his fitness regimen remains simple — consistent exercise, disciplined nutrition and one reliable reality check every time he puts on a pair of pants.