The quickest way to change the temperature scale
Most Honeywell thermostats let you switch between Fahrenheit and Celsius in the settings menu. The exact steps depend on which model you own — some use physical buttons, others use a touchscreen — but the setting is always called "Scale" or "Temperature Scale" and lives in the same general area of the menu system.
If you have the original paperwork or box, check the model number there first. If not, look on the thermostat itself — the model number is usually printed on the back or inside the battery compartment. Knowing your model saves time because the button sequences differ.
Key Takeaways
- The temperature scale setting is found in the Settings or Preferences menu on nearly all Honeywell models, usually labeled "Scale" or "Temperature Scale".
- Digital display models typically require you to hold the Menu button, navigate with arrow buttons, and select the scale option.
- Touchscreen models usually have a Settings icon (gear symbol) that opens a menu where you can tap the temperature scale option directly.
- Once you change the scale, the thermostat will display all temperatures in the new unit when ready, and the change persists even after power loss.
Steps for button-based Honeywell thermostats
If your thermostat has physical buttons and a small digital display, follow this sequence. Press and hold the Menu button (usually on the left side) for about three seconds until the display changes and shows menu options. You should see words like "Settings" or "Preferences" appear on screen.
Use the up and down arrow buttons to scroll through the menu until you see "Scale," "Temperature Scale," or sometimes just "°F/°C." Press the right arrow or Select button to enter that option. The display will show your current setting — either F or C — and a choice to change it. Press the arrow buttons to toggle to the other unit, then press Select to confirm. Press Menu again to exit and return to the normal display.
Steps for touchscreen Honeywell thermostats
Touchscreen models, including the Honeywell Home T9 and similar recent models, have a gear icon or "Settings" label visible on the main screen. Tap that icon to open the settings menu. Scroll down through the options until you find "Temperature Scale," "Scale," or "Display Units."
Tap that option and you will see two choices: Fahrenheit (°F) and Celsius (°C). Tap whichever you want to use. The thermostat will confirm the change and return to the main screen, now displaying temperatures in your chosen unit. The change takes effect when ready.
What happens after you change the scale
Once you switch the scale, every temperature on the display converts when ready — set points, current room temperature, and any scheduled temperatures all show in the new unit. If you had programmed the thermostat to heat to 72°F, it will now display that as approximately 22°C, and the heating behavior stays the same.
The setting is stored in the thermostat's memory, so it survives a power outage or battery replacement. If you lose power for an extended time, the thermostat may reset other settings (like the time or day), but the temperature scale choice usually remains.
If you cannot find the scale setting
Some older Honeywell models do not allow you to change the scale through the menu — the unit was manufactured for one region and locked to that setting. Check your thermostat's model number and search the Honeywell support website for the manual. The manual will state clearly whether scale switching is supported on your specific model.
If the manual confirms the feature exists but you still cannot locate it, try holding down the Menu button for five to ten seconds instead of three. Some models require a longer hold to access a hidden settings layer. If that does not work, the battery may be low — replace the batteries and try again.
Common mistakes that prevent the change from working
The most frequent issue is pressing the wrong button or exiting the menu before confirming the selection. If you press Menu to exit before you see a confirmation message, the change may not save. Always wait for the display to show the new scale or return to the main screen showing temperatures in the new unit before assuming the change took effect.
Another common problem is confusing the scale setting with other temperature-related options like "Setpoint" or "Offset." The scale setting changes the unit itself (F to C or C to F), not the temperature value. If you accidentally changed a different setting, go back into the menu and look specifically for the word "Scale" or the symbol °F/°C.
Honeywell models and where to find the manual
If you need the exact steps for your model, visit the Honeywell Home website and search for your thermostat's model number in their support section. Common models include the T4, T5, T6, T9, and the older programmable models like the RTH6360. Each has a downloadable PDF manual that shows the menu structure and button sequences for your specific unit.
You can also call Honeywell customer support at the number on your thermostat or in the original documentation. They can walk you through the steps over the phone if you are unsure which buttons to press.
Frequently Asked Questions
Will changing the scale affect my heating or cooling settings?
No. The thermostat converts the display only, not the actual operation. If it was set to heat at 72°F, changing to Celsius will show 22°C, and the heating will still trigger at the same temperature. The comfort level stays identical.
What if I change the scale and the display goes blank?
The thermostat may have entered a different menu mode. Press Menu or the back button to exit, wait a few seconds, and try again. If the display remains blank, check that the batteries are fresh and installed correctly. A low battery can cause display glitches.
Can I change the scale on a Honeywell thermostat without the remote?
Yes. The scale setting is in the thermostat itself, not the remote. Use the buttons on the physical unit. If your model came with a remote, the remote may also have a menu option to change the scale, but it is not required.
Does the scale setting change if I reset the thermostat?
Most resets preserve the scale setting, but a full factory reset may return it to the default. Check your manual for the difference between a soft reset (power cycle) and a factory reset before you proceed.
My thermostat shows both F and C on the display. How do I remove one?
That display mode is usually a temporary view during the scale-change process. Complete the steps to select your preferred scale and confirm the selection. Once you exit the menu, only your chosen unit should display.