The independent assessment of RBG Kew's value is found in a new Oxford Economics report (PDF), which highlights the many contributions the 257-year-old institution makes to the UK.
Each of the UK's estimated 29,700,000 taxpayers paid 90p in 2014/15 towards Kew's upkeep, or just under £27m in total. A return of £182m on that investment shows Kew is "excellent value" for money, according to director Richard Deverell.
The £182m includes economic value generated by visitors to Kew and its sister gardens at Wakehurst, and the societal value generated by its contribution to education and scientific research. In 2014/15, more than 1.5 million visitors, including 85,000 school children, visited the two gardens.
The report also quantifies the value to science of Kew's vast work as a global resource for plant and fungal knowledge. Kew's unique combination of extensive collections, databases, scientific expertise and global partnerships was valued at £56.2 million to the UK for 2014/15. This does not include the international value of scientific research carried out at Kew, which is thought to be "substantial".
Deverell said the report comes "at a critical time for Kew".
"We have been focusing our efforts across the organisation on unlocking why plants and fungi matter to the future of our planet and communicating that as widely as possible.
"Having our impact quantified in this way highlights the importance of Kew to the UK economy. It also highlights the difficulty in capturing all the value that Kew delivers in a single number, especially internationally in supporting development or environmental protection overseas.
"For example, our work with 3,000 Madagascan subsistence farming households could help increase resilience to climate change in one of the poorest nations on Earth. The Millennium Seed Bank, the world's largest ex-situ plant conservation project, has the potential to deliver many billions of pounds of value. When you consider all this in the round, I believe we deliver excellent value for the UK taxpayer."
Kew's government funding comes from Defra, and other income is generated through donations, memberships, events and partnerships.
"Secure public funding allows us to leverage further commercial and charitable income. We've raised over £10m in non-government income for Kew Science through grants and private donations with over 130 projects underway. We've also increased the number of visitors to Kew and Wakehurst and hosted commercially successful events like Christmas at Kew," Deverell added.
In 2015 alone, Kew scientists and their collaborators from around the world published 149 species of plants and fungi new to science. The new species include crop wild relatives, sources of essential oils, sources of antibiotics and other medicinal compounds, potential new timbers, ornamental plant species for gardens and conservatories, and fungal species that underpin coniferous forest ecosystems in the North Temperate Zone.
"The range of work being done by Kew's science teams on any given day is astounding," said Kathy Willis, director of science at Kew. "This attempt to quantify our value to society is ambitious but also important in recognising our contribution as well as in raising public awareness at a time when we face so much competition for limited resources.
Ian Mulheirn, director of consulting at Oxford Economics, said: "Our study quantifies the full range of value generated by RBG Kew. Modelling allowed us to put a value on everything from how much visitors benefit from their trips to Kew, to the immense scientific contribution of this historic institution.
"Our results show that the value created by Kew for the whole of the UK outstrips its costs many times over."