I'm assuming an IQ distribuition with a mean of 100 and a standard deviation of 15 (μ=100, σ=15). That's what most modern IQ tests use. If your test is based on a different distribution, subtract the mean of your test (this will probably still be 100), divide by the σ of your test, multiply by 15 and add 100.
E.g., if your test uses μ=100, σ=12 and your score is 140, do:
140 - 100 = 40 40 / 12 = 3.33 3.33*15 = 50 50 + 100 = 150
In this case, 150 would be your score translated to μ=100, σ=15.
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