An adapter for a T12 fluorescent light fixture that is used to convert the fixture into a T5 or T8 fixture. The adapter includes a male input for receiving power supplied by the T12 ballast. The adapter has circuitry that adjusts the power supplied by the T12 ballast to parameters usable by a T5 or T8 fluorescent lamp. Also, the adapter includes a female output for outputting the usable power from the circuitry. The usable power drives the T5 or T8 fluorescent lamp.