Quick answer
To know whether a room is humid enough to grow mould, a simple digital hygrometer that shows relative humidity is all you need, and the TempPro TP49 is our pick: an Amazon Best Seller rated 4.5 stars across 20,712 Amazon.co.uk ratings, reading 10–99% humidity and refreshing every 10 seconds. Aim to keep rooms between 40% and 60%. If you want daily highs and lows, the ThermoPro TP53 records them.
Condensation and mould follow humidity, and you cannot judge humidity by feel. A hygrometer shows the relative humidity of a room so you know when to open a window, run the extractor or switch on a dehumidifier, and whether that dehumidifier is doing its job. They are cheap enough to put one in each bedroom and the bathroom. These four were read on Amazon.co.uk on 15 October 2026 and carry some of the largest numbers of buyer ratings in the category.
Our picks
Pick 1 · Best overall, Amazon Best Seller
TempPro TP49 Digital Hygrometer and Thermometer
Best for: One in every bedroom to spot rooms that need ventilating.
Check price on Amazon.co.ukThe TP49 is the hygrometer most UK buyers choose, and it does the one job that matters: show humidity at a glance. Above 60% for long periods, mould becomes likely. Put one on the outside wall side of each bedroom rather than next to a radiator, which reads artificially dry. ThermoPro has renamed itself TempPro, so the unit that arrives may carry either name.
Pros
- Clear comfort icons
- Stand, magnet or wall mount
- Long battery life
- Compact
Cons
- No backlight
- No min/max memory
Key specs (from the listing)
- Humidity range:
- 10–99% RH
- Temperature range:
- -50 to 70°C
- Refresh:
- Every 10 seconds
- Comfort indicator:
- Dry, comfort, wet icons
- Mounting:
- Stand, magnet, wall slot
- Battery:
- At least 1.5 years (listing)
Pick 2 · Best with min/max records
ThermoPro TP53 Digital Hygrometer
Best for: Bedrooms where condensation builds overnight.
Check price on Amazon.co.ukCondensation is a night-time problem: humidity peaks in a closed bedroom in the early hours, and you would never see it on a single daytime reading. The TP53's 24-hour maximum shows that peak. If the overnight high regularly passes 70%, open a trickle vent or leave the door ajar. The touch backlight helps if you want to check it in the dark.
Pros
- Shows overnight humidity peaks
- Backlight for reading in the dark
- Multiple mounting options
Cons
- Slightly larger than the TP49
- Battery life not stated on the listing
Key specs (from the listing)
- Records:
- 24-hour and all-time max and min humidity and temperature
- Backlight:
- Touch-activated
- Comfort indicator:
- Yes
- Mounting:
- Tabletop, wall, magnet
- Battery:
- AAA
Pick 3 · Most accurate stated, Amazon Best Seller
TempPro TP157 Digital Hygrometer
Best for: Wardrobes, cupboards and checking a dehumidifier's own reading.
Check price on Amazon.co.ukThe TP157 is the only pick here whose listing states humidity accuracy, at ±2 to 3%. That makes it useful as a check against the built-in sensor on a dehumidifier, which reads the air right next to the machine. It is small enough to put inside a wardrobe or under-sink cupboard, the places where moisture absorbers are working.
Pros
- States its accuracy
- Very small for cupboards and wardrobes
- Long battery life
Cons
- Small digits are harder to read across a room
- No min/max
Key specs (from the listing)
- Accuracy:
- ±0.5°C, ±2–3% RH (listing)
- Refresh:
- Every 10 seconds
- Comfort indicator:
- Dry, comfort, humid icons
- Mounting:
- Stand, magnet, hanging hole
- Battery:
- 18–24 months
Pick 4 · Largest display
NOKLEAD Indoor Thermometer Hygrometer
Best for: Living rooms and kitchens where you want to read it from across the room.
Check price on Amazon.co.ukIf the hygrometer will sit on a kitchen counter or a living room shelf, the NOKLEAD's 3.34 inch display is the easiest to read from a distance, and it doubles as a clock. Battery life is shorter than the TempPro models at eight to twelve months per coin cell. The comfort icon gives a quick dry, comfort or wet verdict.
Pros
- Big, easy-to-read screen
- Shows time as well
- Three mounting options
Cons
- Shorter battery life
- Uses coin cells rather than AAA
Key specs (from the listing)
- Display:
- 3.34 inch LCD with clock
- Humidity range:
- 10–95% RH
- Temperature range:
- -9.9 to 60°C
- Refresh:
- Every 10 seconds
- Mounting:
- Stand, magnet, adhesive
- Battery:
- 2 × CR2032, 8–12 months each
Buying guide
What humidity should a home be?
Most UK guidance puts healthy indoor relative humidity between 40% and 60%. Above 60% for long periods, dust mites thrive and mould can start on cold surfaces; above 70% you will usually see condensation on windows. Below 40%, air feels dry and static builds up. Bathrooms will spike after showers, which is normal if they fall back within an hour.
Where to place a hygrometer
Put it at head height on an inside shelf or wall, away from radiators, windows, kettles and direct sun, which all distort the reading. In a damp bedroom, a second one near the cold outside wall shows how much wetter that corner is. Give a new hygrometer half an hour to settle before trusting the number.
Accuracy and checking
Budget hygrometers typically read within a few percent, which is fine for spotting damp rooms. If two units disagree, check them side by side; the salt test (sealing the hygrometer in a bag with a damp pile of table salt, which settles at about 75%) is a well-known way to check calibration at home. Min and max records are more useful than perfect accuracy, because they reveal overnight peaks.
Who does not need a hygrometer
If your dehumidifier already shows room humidity and you only have one problem room, a separate hygrometer is optional, though it is useful for checking the dehumidifier. If walls are visibly wet or mould is spreading, skip the measuring: the room is too humid, and the money is better spent on a dehumidifier and ventilation.
Questions people ask
What is a good humidity level for a house in the UK?
Between 40% and 60% relative humidity. Above 60% for long spells encourages condensation and mould, especially in winter. Bathrooms and kitchens can rise higher briefly after cooking or showering, which is fine if they drop back within the hour.
Are cheap hygrometers accurate?
Cheap digital hygrometers are usually accurate to within a few percent, which is enough to spot a damp room. The TempPro TP157 states ±2–3% RH. Comparing two units side by side is an easy check.
Where should I put a hygrometer in my house?
In the rooms where damp is most likely: bedrooms, the bathroom and any room where washing dries. Place it away from radiators, windows and kettles, at roughly head height, and give it half an hour to settle.
What humidity level causes mould?
Mould growth becomes likely when humidity stays above about 70% at a surface, which can happen on a cold wall when the room reads 60% or more. Keeping rooms below 60% prevents most growth.
How do I lower humidity in my house?
Run extractor fans when showering and cooking, open trickle vents, dry washing with a dehumidifier in a closed room, and keep furniture a few centimetres off outside walls. A dehumidifier set to 50% lowers humidity fastest.