The umbrella organisation calculated the figure for the first time for The UK Civil Society Almanac 2008, which is published today.
Previous almanacs analysed only charities, but this year's edition includes social enterprises, independent schools, universities, cooperatives, trade unions, political parties and housing associations to encompass all of civil society in 2005/06.
It paints a picture of a society in rude health, consisting of 865,000 organisations employing 1.35 million people and with combined assets of £196bn, 3 per cent of the UK asset base. This does not include the value of religious buildings or assets such as London's Tower Bridge, which cannot be sold.
"Civil society organisations have a unique place in securing the nation's heritage, over and above their substantial asset base," the 120-page almanac says.
The volume also suggests that the idea that charities develop out of need is a myth: they are more likely to be found in affluent areas, it says.
Charities had an income of £31bn, up 10 per cent on the previous year. This was largely due to an increase in earned income from goods and services, including contracts, which exceeded 50 per cent for the first time.
Yorkshire and the Humber outstripped other regions in terms of income growth with a 35 per cent increase. The south west was next at 16 per cent. The north east, which experienced a 3 per cent drop, was the only region in England where income fell in 2005/06, but Wales experienced a 4.6 per cent decline.
More than half of charities got no income from the state. "This contradicts suggestions that charities are an arm of government that is largely funded by the state in return for carrying out its wishes," the almanac says. However, 30 per cent of charities were heavily reliant on government funding.
Despite a booming income, there were some "worrying" trends: individual giving rose modestly, grant income was flat and the growth in investment income was down.
"The sector is doing well, but there are lots of charities in need of help," said Oliver Reichardt, research manager at the NCVO.