I'm so excited to answer this one because I'm asked it so much! On all modern IQ tests, the average is 100. This is calculated such that for every age, the average is always 100, even though the expectations of the test go up. The large majority of people will score between 85 and 115, so anything within these is pretty typical and all that you need.
By the way, this also means that the rumors swirling around the internet of who has an IQ "Over 200!" and whatnot, are probably false. Up past 137 or 138 we're all ready splitting the top 1% into tiny little bits, so it just becomes statistically improbable that this many celebrities and children have actually scored that high.