If one takes many online IQ tests you get a quite good picture. Even if you take official tests, your results will vary somewhat. It is a problem that different tests use different standard deviations though. Let's say a person score 130 on an IQ test with SD=15 and scores 148 on an IQ test with SD=24. That is exactly the same result, but that person might not get that, and dismiss IQ as just being crap, because the results "vary" so much. Of course it is more difficult to measure high IQs, so one can be less certain about those. Anyhow, if you take a lot of online tests and just calculate the average score, I am sure that score will be a very decent indication on what it really is. Personally I just say my IQ is about 125. I think it is foolish to say ones IQ for example is 127. You can never be that certain about it, it is always going to be "ish".