To answer your question, the "72 degrees Fahrenheit=room temperature" is considered from internal body temperatures being 98.6 degrees +/-, thus making the temperature of skin to be around 72-76 degrees Fahrenheit. That is why a temperature around that range is usually comfortable and coined as room temperature.

The American Heritage Dictionary of the English Language identifies room temperature as around 20–22 °C (68–72 °F), while the Oxford English Dictionary states that it is "conventionally taken as about 20 °C (68 °F)". Ideal room temperature varies vastly depending on the surrounding climate.

In science, 300 K (27 C or 80 F) can also be used as room temperature for easy calculations when using absolute temperature. Other common values are 298 K (25 C or 77 F) and 293 K (20 C or 68 F). For climate control, a typical room temperature range is from 15 C (59 F) to 25 C (77 F).

Everyone has a different idea about the recommended house temperature. When you're away from home, the suggested thermostat temperature in winter is somewhere between 62 and 66 °F. In reality, the average range is anywhere between 68 and 76 degrees Fahrenheit.