We can all agree that when someone shares a piece of branded content on Facebook, it’s worth something. But quantifying that value is more difficult.

A Facebook share creates additional exposure for a brand and potentially acts as a vote of confidence among a peer group – but exactly how much does it add to a bottom line?

Eventbrite thinks it has the answer, for its own business at least.

The event ticketing company, which launched a UK office in October, tracked sharing and linking activity within social media – then compared its transactional data.

The results showed that when someone shares one of its UK events on Facebook, this generates £2.25 in additional gross ticket sales on average.

In comparison, a share on Twitter is worth £1.80 and a LinkedIn share is worth £1.24 in extra ticket sales.

Eventbrite’s US data is roughly comparable, though LinkedIn is worth much less per share – suggesting that American consumers don’t see the business networking site as a place to organise events.

Eventbrite VP of marketing Tamara Mendelsohn said the stats are extremely important for the business as events are inherently social.

Events are social occasions, it’s no fun when you go alone. Events also say something about who we are, so people like to share them.”

Facebook first emerged as a key traffic driver for Eventbrite in 2008, so late that year it built a one-click integration with the social network so users could instantly share events.

Facebook is now its number one traffic driver followed by Google and Twitter.

Mendelsohn said that initially the company optimised its site with Google in mind, but changed its entire approach when it saw how well events fit with the word-of-mouth marketing enabled by Facebook.

Social lets you reach a much more targeted group of people, so without knowing it at the start we stumbled across a business that could really use social media to grow.”

Eventbrite’s iOS and Android apps allow users to create free or paid-for events, then control the entire process when mobile – from uploading an invite list to checking people in at the event using a QR code scanner.

Users can also search for events and manage their tickets within the app.

Eventbrite charges users 2.5% of the price of each ticket for paid events in the UK (up to a maximum of £6.50), plus £0.65 for every ticket sold.

Since launching in the UK the business has already seen £7.5m in gross ticket sales from more than 25,000 events, from yoga classes up to music festivals.

Globally Eventbrite’s users organised 458,207 events in 2011 with 20.8m tickets sold, up from 222,353 events and 11m tickets in 2010.