T in the Park celebrates its 20th year this summer, with three days of birthday fun featuring some of the biggest names in music getting under way at Balado near Kinross from lunchtime tomorrow.

The story of how Scotland became home to one of the most high profile and best loved events of its type anywhere in the world is detailed in Russell Leadbetter's excellent piece - but even the most cursory glance at that first bill from 1994 shows how much the event has developed, broadened, and cemented its appeal over the last two decades.

We'll be providing coverage and up to the minute reviews on Herald Scotland over the weekend, but until then, here some facts about Scotland's biggest festival to keep you going:

4: T in the Park is now four times the original size when launched - the first one, held in Strathclyde Country Park back in 1994 had capacity for 17,000 on each of the two days.

5: The festival site temporarily becomes the equivalent of the fifth largest town in Scotland over the weekend, and comparable to the largest city centre.

10: An innovative bar-cup recycling scheme was introduced in 2006 paying a 10p deposit on every empty pint container brought back to a designated recycling point.

17: The number of major awards T in the Park has won over the years, including International Festival of the Year 2013, and a 2009 and 2010 Best Toilets double whammy at the UK Festival Awards - a sweet smelling tribute to the cleanliness and efficiency of the 1000-odd portaloos serving the site every year.

20: T in The Park is Scotland's biggest music event, but is also popular across the UK and further. According to DF Concerts, 20% of the crowd is made up of visitors from outside Scotland, with about 2% attending from overseas. T is also the 20th letter of the alphabet. Like, freaky dude.

36: All the beer sold at T in the Park is brewed just 36 hours before the festival, brought 44 miles to site from Tennents Wellpark Brewery in Glasgow. More than 3 million pints of lager have been consumed at the festival since 1994.

90: The time in minutes the event took to sell out in 2010. Uptake this year has been slightly less wholehearted - organisers are blaming the state of the economy and a string of wet summers for dampening enthusiasm, but the upshot is that there are still tickets available for the first time in years.

200: The number of artists performing at T in the Park across 10 stages and 3 days.

1997: The year the festival moved to its present home at Balado near Kinross.

30,000: The length in meters of fencing used at the T in the Park site, including over 8,500m of perimeter fencing, and 472 flags.

85,000: The number of fans expected on each day – the weekend is also likely to attract up to 70,000 campers, and will be kept running smoothly by 7,000 staff.

2.5 million: The number of tickets sold for T in the Park since the festival began 20 years ago.

40 million: The festival's overall worth to Scotland in 2011, in terms of combined economic and media impact, was estimated at more than £40 million, compared with the previous figure of £18m in 2005. The festival's economic impact on Scotland is now thought to run to £10m every year.

100 million: Estimated record sales for Saturday's headliner Rihanna. The Killers (Sunday) are no slouches either, with an estimated 20 million albums sold worldwide. In spite of topping the UK charts again after a triumphant Glastonbury, Friday's Mumford and Sons have a way to go with a meager 6-7 million. Which, you know, they’re absolutely fine with.