This is up from the $7 million found after the last survey which was done two years ago.
Hugh McIntyre, chairman of the Otago Chamber of Commerce Central Otago Advisory Committee, said the $12 million was a "very significant figure" for the region's economy. However, he thought most of the 23% increase could be explained by food, accommodation and hire fees going up.
"But we are seeing a few more people doing the additional trips that are available ... there are more things to do on the trail now," he said.
Directly, the trail contributed just over $8 million and created the equivalent of 121 full-time jobs. This is up from $4.7 million and 60 full-time jobs in the previous survey.
Central Otago District Council business development manager, Jonathan Gadd said this was a 61%-78% increase on the economic and social impact derived from the 2008-09 survey.
He said there were two main drivers of this increase - the amount people spent while on the trail and the number of people doing the trail.
His report on the survey will be considered by the council today The "typical rail trailer" was a person in their 40s or 50s from a larger urban area in New Zealand. International visitors, who account for 20% of rail trailers, tended to be younger, as did rail trailers from Otago, Mr Gadd said.
The Taieri Gorge Railway, curling and visiting gold-mining towns were major activities undertaken by visitors, but entertainment and retail were only minor beneficiaries of the tourist dollar, accounting for 5% of the economic impact.
The largest impacts were in the areas of accommodation, package operators, food and consumables.
Chairwoman of the rail trail trust, Daphne Hull, said the figures were "excellent news".
"It's really great considering this is a time of recession. It's great to see the rail trail benefiting from people coming to the area and seeing the opportunity for a different, cheaper kind of holiday."
The main direction for travel on the trail was from Clyde to Middlemarch (72% of people).
People travelling the opposite way tended to do it faster and spend less.
Half of those doing the rail trail, do so during March and April, but the survey shows usage is starting to spread out over the year.
It was previously estimated that the trail contributed 0.5%-1% to the local economy.
That is now estimated to be 1%-2%.
The survey was conducted at three different times (spring, summer and autumn) between May 2010 and April 2011 at Seagull Hill near Wedderburn, the highest point of the trail with 648 people.
The survey cost $7000.
