I have the same issue, T315 reads 71% humidity, calibrated monitor from work reads 57%. So I purchased Govee equivalent as this has an option to calibrate the temperature and humidity readings.

  @Andy653 I also have a govee temp sensor, they are good, but lack any integration with Google home, which I need.

Totally agree - urgently needed!

For a "high accuracy sensor" as advertised this is extremely poor.

Mine is actually about 2° off temperature - so what good is a thermometer or temp/humidity sensor if it actually shows you the wrong value?

With 2 degrees off I might as well just take a guess...

Interestingly on the heating thermostat KE100 it's possible to set a temperature offset - only in full degrees but at least this way it's possible to bring it within half a degree of the actual temperature.

So let my add in general and for future devices: ANY temperature/humidity sensor should have a calibration function.

Regarding accuracy of this calibration/offset please see this feature request:

https://community.tp-link.com/en/smart-home/forum/topic/646348

! yep. much needed. Bought 6x Tapo T310 sensors. The sensors are not calibrated well enough. +/- 5% RH +/-0.8C in the bunch. But they are clustered around the correct values from my well behaved lab sensors.

  @Johnpigg 

I bought multiple devices and put them next to each other. 10% difference in humidity read out. and 0.9° in temperature.

either calibrate them in the factory or provided a tool