Hygrometer test: which one measures accurately?

HM 16 and HM 22 side by side

Fogged-up windows in the morning^[1], laundry that will not dry in your home, a cellar that smells musty: if you know these signs, you first want to know how humid your rooms actually are. This guide shows you how accurately a home hygrometer measures and which Beurer thermo-hygrometer on beurer.com suits your room. We offer two dedicated measuring devices for this: the HM 22 and the HM 16.

Both devices belong to the thermo-hygrometer product group and measure relative humidity as well as room temperature. They do not humidify or dehumidify themselves; they display values, and that is exactly their job when the air is too humid: they provide the number that lets you assess whether action is needed in your room. Neither model is a medical device, and both come with a 3-year warranty. For an overview of the entire range, see our hygrometer category.

The differences may sound small, but they matter in everyday life: the HM 22 is aimed at anyone who wants to use date, time and a timer in addition to humidity, while the HM 16 is for anyone who wants their values classified straight away without doing the maths themselves. How accurately both devices measure and what the tolerance specification means for this is explained in the next section.

Measuring accuracy and what the tolerance means

No household hygrometer measures humidity accurate to the second decimal place, so an honest comparison starts with the tolerance. For the HM 22 and the HM 16, the manufacturer's product data sheet (as of 11.09.2026) states identical values: the measuring accuracy for relative humidity is ± 5 % in the range from 40 to 80 %, and ± 8 % in the edge ranges from 20 to 40 % and from 80 to 95 %^[3][2]. For temperature, the deviation is ± 1 °C in the range from 0 to 40 °C, and for the HM 16 additionally ± 2 °C at 40 to 50 °C^[3].

In practice, the ± 5 % tolerance works like this: if the HM 22 or the HM 16 shows you 60 %, the actual relative humidity lies somewhere between 55 and 65 %. At the edges of the measuring range, this window becomes wider. That is not a weakness of this one device, but the normal accuracy class of thermo-hygrometers for home use.

For your decision, this accuracy is sufficient in everyday use: you read trends from the hygrometer, not decimal places. Whether your home stays permanently in the comfortable range or the humidity climbs towards critical values can be reliably read from it. The only thing that matters is placing the device correctly and giving it a short settling time after moving it; more on that below.

Display, smiley indication and extra functions

The operating features are where the HM 16 and the HM 22 differ most clearly. The HM 16 classifies the measured values using a smiley indication: a smiling face appears when the temperature is between 20 and 25 °C and the relative humidity is between 30 and 60 %, in other words in the range we consider ideal. A sad face indicates that the humidity is above 60 % at any temperature, meaning the air is too humid. (A neutral face appears when the air is dry, below 30 %). In addition, the HM 16 stores the minimum and maximum readings for temperature and humidity, so you can trace peak values that occurred overnight or while you were away. The display measures 7.5 × 5.4 cm.^[3]

• In addition to temperature and humidity, the HM 22 also shows the date and time, so it remains informative even without a separate wall clock.
• A timer of up to 99 minutes with an audible signal allows short-term measurements, for example to observe how quickly the humidity drops again after cooking or showering.
• A battery change indicator gives timely notice when the two AAA batteries need to be replaced.
• At 8.2 × 7.2 cm, the display is the larger of the two and can be read at a glance^[2].

Both display concepts pursue the same goal in different ways: the HM 16 translates the number into a classification, while the HM 22 provides more context around the number. If you want to know whether your room is fine without having to work out yourself where 60 % stands, the smiley display is the more convenient solution. If you want to use the device as a clock and a kitchen or office helper anyway, that speaks in favour of the HM 22.

Measuring range, battery and settling time

The technical specifications of the two devices differ in only two respects. When it comes to the measuring range for relative humidity, the HM 22 and the HM 16 are the same: both measure from 20 to 95 % and thus cover everything that occurs in living spaces. For temperature, the HM 22 goes slightly lower with −10 to 50 °C than the HM 16 with 0 to 50 °C, which matters for unheated rooms in winter, for example.

• Humidity measuring range: 20 to 95 % relative humidity on both devices.
• Temperature measuring range: −10 to 50 °C on the HM 22, 0 to 50 °C on the HM 16.
• Power supply: the HM 22 runs on two 1.5 V AAA batteries, the HM 16 on a 3 V CR 2025 button cell; both are included with the device.
• Placement: both devices have a fold-out table stand and a hanging option on the back for wall mounting.

One point from the HM 22 instructions for use deserves particular attention because it directly affects measuring quality in everyday life: in changing surroundings, the device needs 10 minutes to deliver reliable readings. So if you move the hygrometer from the hallway to the bedroom, wait that long before reading the value. According to the instructions for use, it can also take 10 minutes after the first start-up before the correct temperature and humidity are displayed.

What a hygrometer cannot do

As helpful as a thermo-hygrometer is for monitoring your indoor climate, its limits are just as clear.

• Tolerance: the humidity reading deviates from the actual value by up to ± 5 % or ± 8 % depending on the range, and the temperature reading by ± 1 °C (± 2 °C on the HM 16 at 40 to 50 °C). Individual readings should always be interpreted within this framework.
• Settling time: after being moved to a different location, the device needs 10 minutes according to the HM 22 instructions for use before it delivers reliable readings again. A value read immediately after moving it is not yet meaningful.
• Placement: the device must be protected from direct sunlight and from heat sources such as stoves or radiators that are too close, otherwise these influences will distort the measurement.

The HM 22 and the HM 16 are measuring devices: they show temperature and humidity but do not humidify or dehumidify the air themselves. When the device tells you that something is off, the next step is an action in the room, not a setting on the hygrometer.

The measured humidity only becomes useful once you can put it into context. The German Environment Agency names 65 to 70 percent as the permanent upper limit for relative humidity in living spaces; if the value measured directly at the wall is permanently above 80 percent, the agency recommends briefly airing out several times a day as an immediate measure.^[4] A combination of room temperature and humidity that stays permanently below this upper limit is considered comfortable; the exact guideline values for your home belong in a guide of their own.

If your hygrometer shows values above these ranges over a longer period, the first step is consistent burst ventilation instead of permanently tilted windows, especially after cooking, showering and sleeping.^[5] If that is not enough, for example when laundry dries indoors or in a damp cellar, our devices take over the second stage: a dehumidifier permanently removes moisture from the air, while a humidifier helps when the air becomes too dry in winter. Our guides to both product groups help you work out which device suits your room.

Mould is a limit that explicitly belongs here: if you already discover mould on the window, in the bathroom or under the wallpaper, the hygrometer is not a remediation tool.^[6] It helps you keep an eye on the moisture, but it replaces neither finding the causes nor the remediation itself; both belong in the hands of professionals.

Which hygrometer suits which room

That leaves the choice, and your rooms make it easy. With its date, time and timer, the HM 22 is particularly suited to places where the device stays in view anyway: in the kitchen, where the timer shows after cooking how the humidity drops again, or in the office, where date and time round off the display content. An independent verdict also speaks for this device: stern Kaufkosmos tested it in "Hygrometer-Test: Auf diese Modelle können Sie sich verlassen" (24.03.2026) and placed it 2nd out of 5 hygrometers tested. About the HM 22, the publication wrote (translated from German): "Narrowly beaten, but likewise reliable and recommendable without reservation, is the Beurer HM 22, which has a timer on board as a small extra (for the kitchen, for example)."

The HM 16 is the right choice if you do not want to interpret the values yourself: the smiley display immediately shows you whether temperature and humidity are in the ideal range, and the minimum and maximum display tells you what happened overnight or while you were away. Both devices measure with the same tolerance, offer a table stand and wall mounting, and come with a 3-year warranty, so the decision comes down to the display, not the measuring quality.

The HM 22 is the recommendation if you are here because of fogged-up windows or damp walls: you first need a reliable number and then a device that shows it to you discreetly every day. That is exactly what it is built for: it measures temperature and relative humidity, also shows date and time, and can be integrated into any room with a table stand or wall mounting. You can view the Beurer HM 22 directly on beurer.com and check there whether it suits your room.