Room hygrometers, the smiley face is still smiling at 70 per cent
The short answer
Prices in GBPUSDEUReach row carries the day it was read
Nineteen room thermometers that also read humidity, from one search and the order export, none of them handled here. The small screen that tells you whether the bedroom is dry enough, and whether the window will be running with water in the morning.
Nineteen listings and about ten designs. The face on most of them is optimistic, so the number underneath is the thing to read.
Which you are buying
| What the photographs show | Listings |
|---|---|
| A small square with a smiley face, about 4.5cm across | 6 |
| A stand with an orange backlight, or a plain one with a face marked OK | 2 |
| A desk clock with a blue backlight, or the HTC-1 clock with a memory | 2 |
| A flat wall display, or a large clock display | 2 |
| A small rounded square, with a face or without | 2 |
| An e-ink sensor that keeps a history in an app | 1 |
| Round minis for a car or a box | 1 |
| An analogue wall dial | 1 |
| Not hygrometers: a window thermometer and a probe thermometer | 2 |
The small square is the one most people end up with, sold singly and in packs of three, five and eight under six listings. It does the job, and which listing you buy it from matters less than knowing what its face means.
The face
Every listing that explains its face gives it the same happy band, a smile from 40 to 70 per cent humidity, with a straight mouth or a frown either side of it. Housing advice on condensation puts a good winter range at 30 to 60 per cent, and says mould is likely when the air sits at 70 per cent or more for long periods. So the smile runs right up to the line where the trouble starts.
The charts do not always agree with themselves either. One listing calls 40 to 70 per cent comfortable and anything over 60 humid on the same panel. Another draws its frowning face beside the words comfortable, 10 to 39 per cent. Read the number. In winter, a bedroom that wakes up above 60 per cent most mornings wants more air, and one that sits above 70 wants it soon.
How close is the number
| Humidity accuracy, from the listings’ own panels | |
|---|---|
| The best overall pick | plus or minus 5 per cent |
| The flat wall display | plus or minus 5 per cent |
| The small square, between 50 and 70 per cent | plus or minus 5 per cent |
| The small square, between 30 and 50 per cent | plus or minus 8 per cent |
| The other fourteen hygrometers | not stated |
Plus or minus 5 means a meter reading 60 could be telling you 55 or 65, and two of them on the same shelf could honestly disagree by ten. That is fine for spotting a damp room and no good for arguing about a few per cent.
The way to know your own meter is the salt test. Put a capful of table salt in a bottle top, add a few drops of water until it is damp like wet sand but not dissolved, and seal it in a food bag with the meter, out of the sun. Leave it overnight. The air in the bag settles at 75 per cent, so whatever the meter reads before you take it out, the difference is its error. Write it on the back.
The range on the title
Three listings of the small square say minus 50 to 70°C, and a fourth listing of the same design prints a panel saying it shows LL below minus 10°C and HH above 50°C. Minus 10 to 50 is the honest range, and it covers every room in a house. None of these is for a freezer or a car left out in a frost.
What was left out, and why
The window thermometer and the probe thermometer are left out because they measure temperature only, whatever their titles say. The blue backlit desk clock is left out for a chart that calls the same reading comfortable and humid. The analogue wall dial is a decoration with a small humidity dial set into it and no accuracy figure. And among the six listings of the small square, only the cheapest could be a pick.
Side by side
Prices in GBPUSDEUR. Each row carries the date its price was read.
| Product | Price | Why it is here | Where to buyLink |
|---|---|---|---|
| Best overall, with a memory and a stated accuracy LCD Digital Hygrometer Room Thermometer With Stand | £6.96$9.28€8.18checked 18 Oct 2026 | A black or white stand with large digits and an orange backlight that comes on at a touch, and a high and low memory for both the temperature and the humidity. Its own panel gives an accuracy, plus or minus 1°C and plus or minus 5 per cent humidity, a resolution of 0.1°C and 1 per cent, and a fresh reading every ten seconds. It stands on a desk, holds to the fridge by a magnet or hangs from a hook | Check opens in a new tab |
| The cheapest, with the most honest panel 2025 New Mini LCD Digital Thermometer Hygrometer | £0.57$0.75€0.67checked 18 Oct 2026 | The small square with a smiley face, 44mm across and 11mm deep, sold under six listings here, and this is the cheapest of the six. Its own panel says the temperature is about 1 to 2°C out, the humidity plus or minus 5 per cent between 50 and 70 and plus or minus 8 between 30 and 50, and that it is not a measuring tool. For telling a dry room from a damp one that is enough. Check it against salt before trusting the last few per cent | Check opens in a new tab |
| A desk clock with a high and low memory Digital LCD Thermometer Hygrometer Humidity Meter | £4.85$6.25€5.70checked 18 Oct 2026 | The HTC-1, a large black and white display with the temperature, the humidity and a clock with an alarm, on a fold out stand or a hook. Its memory button shows the highest and lowest temperature and humidity it has recorded, which in a bedroom is the overnight peak. It does not state an accuracy | Check opens in a new tab |
What you can settle before you buy
- Read the number, not the face. Housing advice puts a good winter range at 30 to 60 per cent and says mould is likely when the air sits at 70 per cent or more for long periods. Every face here is still smiling at 70.
- Get one that remembers the high. Condensation builds overnight with the door shut, while nobody is looking. A meter with a high and low memory shows the peak you slept through, and the best overall pick and the HTC-1 clock both have one.
- Check it with salt. A capful of table salt with a few drops of water, damp like wet sand and not dissolved, sealed in a food bag with the meter overnight, holds the air in the bag at 75 per cent. Read the meter while it is still in the bag: the difference from 75 is its error.
- Put it where you live. Not on the radiator shelf, a sunny windowsill or beside the kettle. The cheapest pick's own panel says its sensor is sensitive to heat at the vent.
What to read twice
- The faces smile all the way to 70 per cent. One listing's own chart calls 40 to 70 per cent comfortable and anything over 60 humid, both at once. Another draws a frowning face and labels it comfortable for 10 to 39 per cent.
- Only three give an accuracy. Two say plus or minus 5 per cent. The cheapest small square says plus or minus 5 between 50 and 70 per cent, plus or minus 8 between 30 and 50, and that it cannot be used as a measuring tool. Two honest meters side by side can disagree by ten.
- The temperature range on the title is not the one on the panel. Three listings of the small square say minus 50 to 70°C. The same design's own panel says it shows LL below minus 10°C and HH above 50°C. For a room that is plenty, and for a freezer it is no use.
- Two are not hygrometers. A round window thermometer and a fridge thermometer on a probe are sold with hygrometer and humidity in their titles. Neither reads humidity.