Temperature accuracy

I am wondering about the temperature accuracy. On ruuvi.com I found the following

  • Temperature sensor accuracy
  • Typical absolute accuracy ±0,5 °C @ 25 °C
  • ±1 °C @ 0-25 °C
  • output resolution 0,01 °C

On bonsch-sensortech.com I found, for BME280 (in RuuviTag, right?)

  • 0.5 °C at 25 °C
  • 1.0 °C at 0…65 °C
  • 1.25 °C at -20…0 °C
  • 1.5 °C at -40…-20 °C

I had put the RuuviTag in my freezer, set at -18 °C, and the RuuviTag showed -28.5 °C. I thought the freezer’s thermostat should be more accurate than that, doubting the RuuviTag, but then another RuuviTag next to the first one showed -27 °C, making me wonder if the freezer has a problem.

I also found some old posts saying that the RuuviTag has a 5 °C accuracy at sub-zero temperatures but Bosch claims a better. I assume the to-be-launched RuuviTag Pro is more reliable, but what is the latest on RuuviTag temperature accuracy?


Bosch datasheet is the authoritative document on temperature accuracy. We have some variants with SHTC3 and TMP117 sensors providing temperature data, but as far as I know every unit we have sold through webshop so far has BME280.

Placement of sensor in freezer and refrigerator makes a huge difference, and many coolers experience pretty wild temperature swings.