Billie Eilish has admitted she does not know the price of many household items and thought a box of cereal cost 35 US dollars.

The 19-year-old singer told Vanity Fair that during lockdown she had mistakenly ordered 70 small boxes of Froot Loops to her home.

Eilish, who last year made history by sweeping all four major categories at the Grammy Awards, said that her age meant she was in a “really weird position”.

Her number one debut album, entitled When We All Fall Asleep, Where Do We Go?, was released in 2019 when she was aged 17, shooting her to international fame.

She said: “I don’t know what things cost because I’ve never been an adult before. And, you know, I grew up with no money.

“It’s a really weird position I’m in. I feel kind of stupid because I’m like, I don’t know how much Froot Loops are.

“I tried to order one box of Froot Loops and I was like, Oh yeah, sure. It’s 35 dollars (£25). I didn’t know that that’s expensive. I ordered 70 boxes.”

The 92nd Academy Awards – Vanity Fair Party – Los Angeles
Billie Eilish and her brother Finneas O’Connell (Ian West/PA)

Eilish also addressed the scrutiny she has faced online over her body image, after a paparazzi photo circulated online showing her on the way to the beach wearing a vest, prompting negative comments from some.

She said: “I think that the people around me were more worried about it than I was, because the reason I used to cut myself was because of my body.

“To be quite honest with you, I only started wearing baggy clothes because of my body.

“I was really, really glad though, mainly, that I’m in this place in my life, because if that had happened three years ago, when I was in the midst of my horrible body relationship—or dancing a ton, five years ago, I wasn’t really eating. I was, like, starving myself.

“I remember taking a pill that told me that it would make me lose weight and it only made me pee the bed—when I was 12. It’s just crazy.

“I can’t even believe, like I—wow. Yeah.

“I thought that I would be the only one dealing with my hatred for my body, but I guess the internet also hates my body. So that’s great.”

Eilish will feature in a documentary titled The World’s A Little Blurry, which follows her during the recording and release of her acclaimed debut album.

The documentary features the pop sensation’s parents, Maggie Baird and Patrick O’Connell.