These are heady times for India's richest. Thanks to a roaring Mumbai stock market, with a benchmark index up 53 per cent in the past year, and a strong rupee that appreciated 12 per cent, for the first time, all India rich-listers are billionaires. In aggregate, their wealth surged to $351 billion (Rs 13. 8 trillion), a bit more than double last year's $170 billion (6.7 trillion rupees), making India's 40 by far the wealthiest such group in all of Asia.

The four richest Indians are worth an astonishing $180 billion (Rs 7.1 trillion). Steel tycoon Lakshmi Mittal, who lives in London, is No. 1 again, worth $51 billion (Rs 2 trillion), but Mukesh Ambani, whose Reliance Industries [Get Quote] is India's most valuable company, is quickly closing the gap. His net worth jumped $30.5 billion (Rs 1.2 trillion) to $49 billion (Rs 1.92 trillion), making him the year's biggest gainer. His estranged brother Anil is close on his heels, up $30.2 billion (Rs 1.18 trillion) to $45 billion (Rs 1.76 trillion).

In pictures:
India's 40 richest
The top 10 Indian billionaires

Kushal Pal Singh, worth $35 billion (Rs 1.37 trillion) after the listing of his flagship DLF, is now the world's richest real estate developer. Had these four been worth as much in March, when we published our annual list of the world's billionaires, they all would have ranked among the world's 10 richest. Together, the foursome is worth more than the 40 richest Chinese combined.

Twenty-nine of the people who returned to the list are richer than last year. The only exception is Rahul Bajaj, who is battling his younger sibling over dividing their empire, and whose fortune was flat at $2.3 billion (Rs 90.2 billion). Ten newcomers made the cut, including Guatam Adani, who built Mundra Port on India's west coast; Anand Jain, Mukesh Ambani's school buddy; and Gautum Thapar, whose Ballarpur Industries [Get Quote] is India's largest paper maker.

In pictures:
The world's billionaires
Billionaires Asia-Pacific

The red-hot real estate sector churned out a couple more billionaires as well: Niranjan Hiranandani, a surgeon's son, who built a thriving township in suburban Mumbai, along with his brother; and Rakesh Wadhawan, whose July listing of his company Housing Development & Infrastructure made him a billionaire.

A net worth of $1.6 billion (Rs 62.8 billion) was the minimum needed to make the list, up from $790 million (Rs 31 billion) last year. That meant folks like longtime member Naresh Goyal, the founder of Jet Airways [Get Quote], dropped off our list, despite his fortune rising 55 per cent to $1.55 billion (Rs 68.8 billion).

Thirteen other billionaire fortunes missed the cut. They include Nandan Nilekani and Senapathy Gopalakrishnan, co-founders of software services giant Infosys Technologies [Get Quote], and self-made billionaire Jignesh Shah, who built India's largest commodities exchange. Also among this group of just-misses were five newly minted billionaires, including pharmaceuticals entrepreneur Murali K. Divi and India's bullish investor Rakesh Jhunjhunwala.

Besides being rich, one must be an Indian citizen to make this list. As a result, three non-India residents, including Lakhmi Mittal, are included, but construction magnate Pallonji Mistry, Tata Sons' largest shareholder, who has become an Irish citizen, is not.

Unlike our annual billionaires list, this ranking has been broadened to include family fortunes. For instance, Tulsi Tanti's $10 billion (Rs 392.2 billion)fortune represents his family's entire 70 per cent stake in Suzlon Energy [Get Quote], not just his individual 29 per cent stake that's reflected in the billionaire rankings. Net worths were calculated using Nov. 2 market prices and exchange rates. Privately held companies are valued by comparing them to similar publicly traded companies.