That's more than 231 million garments sitting idle nationwide - enough to fill 139 swimming pools or 42 football fields, according to research from the Red Cross and Uber.
"The nation is holding onto billions of dollars worth of clothes that can be helping people in need," Australian Red Cross spokesman Richard Wood said on Saturday.
The companies' annual clothing drive on Saturday in Sydney, Melbourne, Brisbane, Adelaide and Perth collected about 125,000kg of donated garments.
The result was the highest since the event started seven years ago, and a 56 per cent increase on last year.
It's a team effort offering free Uber couriers for pre-loved clothes to Red Cross stores across the country.
"Every item helps stock our Australian Red Cross Shops, which directly fund our humanitarian programs to support some of our most vulnerable communities," Mr Wood said.
The clothing drive, now in its seventh year, aims to remove the main barriers to donating clothes, including that almost two-thirds of people surveyed would give more to charity if it were easier.
"We know that in our busy lives, convenience is often the missing link when it comes to donating clothes," Uber boss Emma Foley said.
The survey of 2000 people also found confusion and time pressure were leading to poor donation habits.
More than a third of respondents admitted to leaving clothes outside an op shop after hours, despite knowing they might be thrown away, and almost one in five admitted to donating items they knew were not quality enough to be sold.
A fifth said they did not donate as they were unsure what items charities would accept.
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