Most Kiwi women own about 12 bras but they only wear five of them regularly - and a quarter are never taken out of the undie drawer at all.
This was just one of many bra-wearing habits revealed in a recent survey of more than 4000 women around the country.
Rose and Thorne lingerie's second annual 'bra census' also discovered eight per cent of Kiwi women wore their bra for a week or longer before popping it in the wash.
Most people will wear a bra four times before washing it.
Rose and Throne director Debra Hall said when they looked into the findings, women said the reason they delayed washing was because of the perception it would wear their bra out.
"One of the interesting things our bra guru said is that actually all of the body lotions and deodorants we use attack the lycra in the bra and it collapses faster than if you wash it more regularly."
Hall said the company decided to run the census again after overwhelmingly positive responses from customers after the first survey ran last year.
"I've got a market research background so I'm very aware of the wonderful things you can find out if you just ask people," she said.
The number of bras owned and regularly worn remained the same over 2015 and 2016, she said.
"That was quite interesting. The other thing that was the same was the most common favourite bra - black and lacy.
"I'm not a fashionista, but from my observation black still appears to be in fashion."
The rise of the active wear trend was also reflected in this year's survey, with around a quarter of all women saying they would wear a sports bra for a purpose other than exercise.
"I have a certain top which I love, it's casual and sporty and looks great with my Calvin Klein sports bra under it," one respondent wrote.
Women mainly picked comfortable and supportive as attributes they looked for in a bra, something Hall said was validating for Rose and Thorne.
"We're after delivering comfort and confidence."
The information gathered in the census would be used to guide the company's future design of bras, available online and in the Warehouse where Rose and Thorne bras are stocked.
"From our perspective you don't have to spend a fortune to get a bra that fits and looks good," Hall said.
"Bras are one of the many things in our lives that have been torturing women for 100 years - it doesn't have to be like this.
"I'm on a mission to change women's lives one bra at a time."