The unpaid work of carers saves the UK £87bn per year - more than the total amount spent by the NHS in the last financial year, say experts.
Carers' impact on the economy is significant
The figure, calculated by the University of Leeds for the charity Carers UK, is up 52% since the last estimate, calculated in 2002.
The average person caring for a sick or frail relative is now estimated to save the nation more than £15,260 a year.
The government said measures had been taken to help carers, with more due.
The new figures are based on how much it would cost to provide alternative care if a carer was not available. This has been calculated at £14.50 an hour.
The total is more than four times the amount spent on social care services for adults and children by local authorities in the year 2005-2006.
Economy too reliant
Carers UK warned that the economy was over-reliant on care provided by family and friends - and if just a small proportion gave up it could have a disastrous impact.
It said many carers remained isolated and unsupported, with thousands living in poverty, unable to take up paid work or have a normal social life.
The charity said health and social care services had failed to keep pace with rising demand.
And the needs of those who required support were also becoming increasingly complex.
It is calling for significant new investment in social care, and a review of carers' benefits, including an exploration of tax breaks to help carers avoid poverty and remain in employment.
Imelda Redmond, Chief Executive of Carers UK said: "It is clear that without carers, our NHS and social care systems would collapse.
"It is ironic, given the billions they contribute to the economy, that so many carers are forced into poverty and a low quality of life.
"We need concerted action from government, employers and public bodies to end social exclusion among carers.
"Carers are invaluable to the UK - it is time they were given the support and recognition to become valued and equal members of society."
Ms Redmond said each year one in five carers gave up work - a loss of skilled workers the economy could not shoulder indefinitely.
A Department of Health spokesman said the government had long acknowledged the crucial role of carers.
The New Deal for Carers initiative had been designed to improve support for and recognition of their work, the spokesman said, and measures such as the provision of emergency respite care had helped.
"We are revising the carers strategy; this is the most far-reaching consultation on the future of carers with the fullest engagement of carers and their families.
"Carers UK's recommendations will certainly be taken into consideration as part of the revision of the strategy."