Hi @Ew thank you for the question! As a general rule of thumb, a temperature more than 37.5 is considered a fever. Some variation may be due to calibration settings, although this crisis has also exposed errors and fundamental flaws in some non-contact thermometers sold online that consistently produce inaccurate readings. 

Use the “probe” type thermometers for a measurement of oral or armpit temperature, which you can purchase from established brands such as Guardian.

That being said, fever is a natural response of the immune system to any trigger of inflammation. If you feel unwell, with or without a measured temperature, and especially if you developed other symptoms, don’t hesitate to review with a medical professional to get personalised advice. Hope this helps!