Things You'll Need
Most thermostats allow the temperature offset to be set from -5 to +5 over the displayed temperature. If the thermostat is off by more than 5 degrees either way, you'll probably have to replace the thermostat.
If the thermostat is in a drafty location or direct sunlight shines on it, you may want to relocate it to an area free of drafts or sunlight, because they alter the accuracy of the thermostat.
Thermostats can sometimes begin to show an inaccurate temperature, which can lead to a room becoming too cold or too warm. If a manual thermostat were to become uncalibrated, you would usually have to replace the entire thermostat. However, today's programmable thermostats come with a setting that allows you to manually adjust the temperature up or down if it is reading wrong. This keeps you from spending money on premature replacements, and helps you save money by keeping your home at the correct temperature.
Purchase a secondary thermometer that is accurate if you already do not have one. You will use this to check the temperature reading against your thermostat's reading.
Place the thermometer right next to the thermostat. Allow it to remain there for 10 to 15 minutes to ensure an accurate temperature reading.
Check if your thermostat's reading differs from the thermometer's. If it does, you'll need to calibrate your thermostat.
Refer to your individual programmable thermostat on how to change the temperature offset of the thermostat. This is typically a menu item on the thermostat screen.
Adjust the temperature offset up or down to match what your thermometer is reading. Once the thermostat is set to this temperature, it will use this new number as the actual temperature of the room and maintain the temperature accordingly.
Elizabeth Knoll has been writing full-time since 2008. She has a deep love for gardening and has spent a vast amount of time researching that subject. Her work appears on various websites. Knoll received a certificate in Early Childhood Education from Moraine Park Technical College.