The quickest way to change the temperature scale

Most Honeywell thermostats switch between Celsius and Fahrenheit through the settings menu on the display itself. The exact steps depend on which model you own — some use a physical button sequence, others use a digital menu — but the process takes under a minute once you know where to look.

The most common route is to press the Menu or Settings button on your thermostat's face, scroll to a Display or Units option, and toggle the scale. If your model has a small digital screen with soft buttons (the buttons below the screen rather than raised), you will navigate using the arrow buttons and confirm with Select. If it has physical buttons on the side or top, you may need to hold one down or press a specific combination.

Key Takeaways

  • Most Honeywell models let you change the temperature scale through a Menu or Settings option on the thermostat's display itself, without touching the wall or calling a technician.
  • Digital-screen models typically use arrow buttons to navigate to Display or Units, while older models with physical buttons may require holding a specific button or pressing a combination.
  • The change takes effect when ready on the display, but your heating and cooling system continues to work the same way — only the numbers you see change.
  • If you cannot find the setting in the menu, your model may require a factory reset or a call to Honeywell support, though this is rare.

Steps for models with a digital display and soft buttons

If your thermostat has a small screen with buttons directly below it (not raised buttons on the face), follow this sequence. Press the button labeled Menu or Settings — usually the leftmost soft button. The screen will show a list of options; use the up and down arrow buttons to scroll until you see Display, Units, or Temperature Scale.

Once you highlight the right option, press the button below it (usually labeled Select or Enter) to open that submenu. You should see two choices: Celsius or Fahrenheit. Use the arrow buttons to select the one you want, then press Select again to confirm. The display will update when ready, and you can press the back arrow or Menu again to exit.

Steps for models with physical buttons on the side or top

Older Honeywell models and some newer ones use physical buttons rather than a menu screen. Look for a button labeled Mode, Set, or Hold on the side or top of the unit. On many models, you hold down the Mode button for three to five seconds until the display flashes or shows a menu.

Once in settings mode, use the up and down buttons to navigate to the temperature scale option. Some models show a small "C" or "F" symbol on the display; press the up or down button to toggle between them. Press Mode again or wait a few seconds without pressing anything to save the change and exit settings mode.

Finding your exact model number and manual

If the steps above do not match your thermostat, the model number is your fastest route to the right instructions. Look on the back of the unit or inside the battery compartment for a number starting with RTH, T, or CM. Write it down or take a photo.

Go to the Honeywell Home website and search for your model number in their support section. Most product pages have a PDF manual with a full menu map and button guide. If the website does not have it, search "[your model number] manual PDF" in a search engine — many retailers and support sites host the documents for free.

What happens after you change the scale

The display will show temperatures in your chosen scale from that moment on. If you had set a target temperature of 72°F and switch to Celsius, the display will show approximately 22°C — the same actual temperature, just in different units. Your heating and cooling system does not change; it still maintains the same comfort level.

If you switch back and forth between scales, the thermostat remembers your target temperature in both, so you will not lose your settings. Some models also let you set different scales for different times of day or different rooms if you have a multi-zone system, though this is less common on basic models.

Troubleshooting if the setting will not change

If you cannot find a Display or Units menu, or if the setting does not stick after you change it, the thermostat may be in a locked mode. Some Honeywell models have a child lock or installer lock that prevents menu changes. Look for a Lock button or option in the menu and try pressing or toggling it off.

If the display still will not change, try removing the batteries (if it is battery-powered) for 30 seconds and reinserting them, or turning off the breaker to a hardwired model for the same length of time. This resets the thermostat without erasing your settings. If none of these steps work, contact Honeywell support with your model number — a hardware fault is rare, but possible.

Frequently Asked Questions

Will changing the temperature scale affect my heating and cooling?

No. The scale change only affects what numbers appear on your display. Your thermostat maintains the same actual temperature you set, whether you read it as 72°F or 22°C. The system works identically either way.

Can I change the scale on a Honeywell thermostat that is controlled by an app?

Yes. If you control your thermostat through the Honeywell Home app on your phone, the scale setting is usually in the app's settings menu under Display or Units, separate from the thermostat itself. You can also change it on the physical thermostat using the steps above, and the app will reflect the change.

What if my thermostat does not have a Menu button?

Some very basic models use only physical buttons for heating and cooling mode, with no settings menu. If yours has no Menu, Settings, or Mode button, check the manual for your specific model — it may require a different button combination, or it may not support a scale change at all. Honeywell can confirm this if you provide your model number.

Does the temperature scale change affect the thermostat's scheduling or programming?

No. Any schedules or programs you have set — like "heat to 68°F at 6 a.m." — continue to work the same way. The thermostat converts the target temperature to whichever scale you are viewing, but the actual heating and cooling behavior does not change.