Use the estimator
Our room temperature calculator gives you an estimate without any measuring. It is a simple model, so treat the result as a ballpark.
Look at things you already have
- A smart thermostat shows the temperature it senses.
- Some AC indoor units show the room temperature on their display. Check your manual. The number on a remote is usually the temperature you set, not the temperature of the room.
- A home weather station or a smart display with a sensor will show an indoor reading.
What about your phone?
A few phones have a sensor for the air temperature around them, but most do not. Many apps that show a temperature are really showing the weather outside, or the temperature of the phone's battery. Neither one is your room temperature. A phone that has been in your pocket or on a charger will be warmer than the room.
Use the weather outside as a clue
A closed room with no AC or heater slowly follows the temperature outside, but it lags behind. It heats up later in the day and cools down later at night. A room with the AC on will move toward the temperature you set, but it usually does not land exactly on it, especially if windows are open or it is very hot outside. If your room feels hotter than the weather, see why a room can be hotter than outside.
How you feel is not a good thermometer
Your body is easy to fool. You feel warmer after walking up the stairs and colder after a shower. Humidity and moving air change how a room feels too. Use your feeling to decide if you are comfortable, not to read the temperature.
The best fix is a cheap thermometer
A basic room thermometer is the most accurate way to know. Put it away from windows, direct sun, heaters, vents and electronics. Give it a few minutes to settle before you read it.
Not sure what number you should aim for? See what is a comfortable room temperature.