Hamilton's inaugural V8 motor race poured $28.3 million into the local economy - a 40% boost on initial predictions, according to an economic analysis.
The Hamilton 400, held in April this year, attracted an estimated 54,450 visitors to the city during the week long event, says hospitality consultant company Horwath HTL.
About 39,050 attended the event itself with the rest being visitors accompanying ticket holders.
They spent $7m on accommodation, $6.8m on food and beverages, $2.1m on merchandise, $3.8m on retail, entertainment and leisure not at the event, $2.2m on local transport and $6.2m for the purchase of goods and services associated with event management.
The resource consent application in 2006 predicted the impact would be around $20m.
Hamilton mayor Bob Simcock said the results of the study were pleasing, especially since they were significantly greater than originally estimated.
The city took on the V8s to enhance our city's reputation and for the economic benefit, he said.
"Clearly hosting the event has delivered economically in year one. More importantly though, the data from the survey gives us reassurance that these benefits will continue for years to come."
He said the research also showed that visitors' perceptions of Hamilton had improved as a result of their stay.
The survey found 84% of visitors said they were either quite or very likely to return next year.
