Delay giving your child an IQ test until he is at least 4 or 5 years old. Tests given at an earlier age tend to be unreliable and can place the child under unnecessary stress. IQ tests given around age 5 can be useful in planning a child's educational future.
Take your child to a professional test administrator. Many schools offer IQ tests, but their test administrators need to be properly trained for the proper uses and limitations of the test given and know how to accurately record and interpret results without bias. Avoid Internet tests or tests given in a collective group since these tests can have widely varied results and are generally not reliable. Many psychologists also can give IQ tests.
Wait for the results from the test administrator. A score of 100 is considered average, meaning that your child's mental development is standard for his age. A score of 150 would indicate that your child has the mental development of someone 1.5 times his age. A score under 100 indicates a slower than average mental development.