The best TFA Dostmann hygrometers, compared.
Top pick: TFA 45.2027 indoor hygrometer – Indoor dial at about £17.39, 4.2 from 1,916 reviews, when a German scale is acceptable and TFA’s English page says synthetic-hair. Best value: TFA 45.2045.02 indoor-outdoor hygrometer – Lowest captured price at about £9.71, 4.2 from 1,248 reviews, when the listing’s job is indoor and outdoor. Updated October 2026.
A TFA Dostmann hygrometer is an analogue thermo-hygrometer: one dial shows relative humidity and temperature. TFA’s English manual treats sustained indoor humidity above 65% RH as a condition that encourages mould, and it says to regenerate an analogue movement at least every six months. The for Energy aims at about 40–60% RH and about 18–21°C. Those figures are not one statute, and 40–60% RH is not a legal limit. A metal ring and a Germany line are not a humidity specification. Only the 45.2045.02 listing says indoor and outdoor, and its country of origin is. If you need a logged alarm or a dew point, use a [hygrometer](/hub/climate-measuring/hygrometer) comparison for that job. It does not measure water in plaster, and it does not repair a building. There is no dew point, no 24-hour trace, and no alarm. Do not treat any of these dials as accurate to 1% relative humidity, and do not apply a ±3% RH tolerance to them.
A TFA Dostmann hygrometer is an analogue thermo-hygrometer: one dial shows relative humidity and temperature.
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Personal buying guide
Question 1 of 2
Where will the dial live?
The TFA 45.2027 is an indoor analogue air-condition monitor at about £17.39, with 4.2 from 1,916 amazon.co.uk reviews. TFA’s English product page calls this model a synthetic-hair precision hygrometer, and the captured amazon.co.uk listing does not name a sensor. The title marks the unit as German, and a UK review says the scale was printed in German. Ten UK reviews mention a sensitive needle and a cheap plastic bezel. Two units disagreed after a wet towel, one salt check sat about 6 % off, one desiccator reading was about 9 % RH high at 20 °C, and one thermometer stuck at 23 °C when it was 0 °C outside. The battery line is in German and states that no batteries are required. Humidity is given as 1–99 % and temperature accuracy as ±1 °C, and the listing does not name a regeneration interval. A greenhouse is asked in a bullet and left unanswered, while the placement line says indoors only. In this comparison it is the top pick when a German scale is acceptable and that English-page synthetic-hair line is why the price is about £17.
Pros
Cons
Best for: An indoor dial when you accept a German scale and you are paying about £17 because the English page says synthetic-hair.
Less suitable: A buyer who needs English words on the scale, or a greenhouse.
Specifications
Common questions
Can this hygrometer be used in a greenhouse?
The listing asks the question and does not answer it. The placement bullet says only place it indoors, and it names the house, a basement, or a garage.
Is it battery powered?
The battery line is the German sentence “Keine Batterien erforderlich”, which means no batteries are required. No cell count is named.
Does the listing show a humidity span?
Yes. The operating-humidity line is 1–99 %, and the bullets name marked comfort zones. They do not print an optimum band.
The TFA 45.2045.02 is the only dial in this set whose listing says indoor and outdoor, at about £9.71 with 4.2 from 1,248 amazon.co.uk reviews. The country-of-origin attribute is China, and the bullets do not say Germany. It asks for regeneration every 6 months, prints coloured comfort zones, and gives a bullet temperature span of −30 to 50 °C, while the lower-temperature attribute says 30 °C. The battery line says no batteries are required, and a separate voltage line says 1.5 V without naming a cell. Only two of the first 50 reviews are from the UK: one arrived working and later had replacement glass sent after a drop, and one had humidity stuck at 100 % or above. That UK sample is too small to treat as what owners think. The temperature accuracy line is ±2 °C, which is wider than the ±1 °C printed on the indoor German dials. In this comparison it is the best value when the job is indoor and outdoor, not when you wanted a German indoor dial.
Pros
Cons
Best for: A dial the listing allows outdoors as well as indoors, at the lowest price in this set.
Less suitable: A bedroom buyer who wanted a German indoor dial, or anyone treating two UK reviews as a consensus.
Specifications
Common questions
Does the listing say this dial can go outdoors?
Yes. The title and the bullets say indoor and outdoor use, and the mounting line says inside mount and outside mount. The bullet temperature span is −30 to 50 °C. The lower-temperature attribute says 30 °C.
Does it need batteries?
The battery line says no batteries are required. A separate voltage line says 1.5 V and does not name a cell.
How often should it be regenerated?
The bullet says the mechanical thermo-hygrometer should be regenerated every 6 months.
The TFA 45.2024 is a small metal-ring dial, about 36 g, listed for indoors at about £10.94 with 4.1 from 3,045 amazon.co.uk reviews captured on 15 October 2026. In the first 50 reviews, nineteen are from the UK, and the praise that repeats is a readable green comfort band and a dial people treat as needing no cell. The battery attribute still says batteries are required and names no type, so the card and those reviews do not tell the same story. Criticism in that UK sample centres on needles that arrived pinned or caught, and on a rear adjustment that did not create confidence. One UK review cites a gap of at least 15 to 20 degrees against a digital meter. The humidity span is 15–100 %, the temperature accuracy line is ±1 °C, and the listing does not name a regeneration interval. The title size and the attribute size are two different figures, so they stay as two measurements.
Pros
Cons
Best for: A small indoor metal-ring dial when you want the largest review file in this set and can live with the battery-line conflict.
Less suitable: A greenhouse, an outdoor wall, or a buyer who needs the listing and the reviews to agree about batteries.
Specifications
Common questions
Does the listing say this hygrometer needs batteries?
The battery line says batteries are required. It does not name the type or the number. The bullets do not say the dial is battery-free.
Can the listing be used in a garage?
The bullet says hang it, and only place it indoors. The places it names are the house, a basement, or a garage.
Does the listing say the body is metal?
The title names a metal ring. The specification table does not give a body material.
The TFA 45.2043.51 is the listing that prints “synthetic-hair precision hygrometer” in the amazon.co.uk bullet, at about £17.96 with 4.1 from 135 reviews. Comfort marks read Dry, Ideal, and wet, the battery line says without a battery, and the bullets allow a wall mount or freestanding use indoors. The sample is small. Two UK reviews in the dump split the picture: one says it is readable at a distance, and one says it cannot be set so that both low and high humidity agree, with a gap of about ±20 %. The attribute table prints both 1 °C and ±2 °C. The temperature attributes say a lower figure of 50 °C and an upper figure of 55 °C, which is not a room range. Regeneration is not named. A greenhouse is asked and left unanswered, while the placement bullet says inside only.
Pros
Cons
Best for: A buyer who will pay about £17.96 so the UK listing itself says synthetic-hair, and who can accept a thin review file.
Less suitable: Anyone who needs a deep UK review sample, or a dial for outdoors.
Specifications
Common questions
Can this hygrometer be used in a greenhouse?
The listing asks the question and does not answer it. The bullet says it is only to be assembled inside, for example in the house, a basement, or a garage.
What sensor does the listing name?
The bullet names a synthetic-hair precision hygrometer. Comfort zones are marked Dry, Ideal, and wet.
Does it need a battery?
The battery line says without a battery. No cell count is named.
The TFA 45.2041.42 is the other small metal-ring indoor dial, listed at about £11.81 with 3.8 from 575 amazon.co.uk reviews, the weakest average in this set. The battery line says no batteries are required, and the bullet asks you to regenerate it regularly without giving an interval. Seven UK reviews in the dump are thin on praise and specific on faults: units arrived rattling, a thermometer that did not work, and both needles loose. The bullet range is 0–50 °C and 20–100 % relative humidity, while the lower-temperature attribute says 18 °C, so those two lines cannot both be the range. The title size is L 120 × W 29 × H 235 mm and the item length is 7 cm, which is a second pair to leave unmerged. The included leaflet says English is not guaranteed. A ±1 °C temperature line is printed, and the listing does not name a sensor.
Pros
Cons
Best for: A no-battery indoor dial only if you will check the pointer and the thermometer on the day it arrives.
Less suitable: The default small German indoor dial, when the 45.2024 carries the larger review file at a similar price.
Specifications
Common questions
Does this hygrometer need batteries?
No. The battery line says it requires no batteries, and no cell count is named.
What measuring range does the listing print?
The bullet says 0 to 50 °C and 20 to 100 % relative humidity. The lower-temperature attribute says 18 °C, which does not match that bullet.
Is the instruction leaflet in English?
The included-components line lists operating instructions and says the English language is not guaranteed.
We compared five analogue TFA Dostmann thermo-hygrometers on amazon.co.uk and scored them from the listing facts in this set. Prices, stars, and review counts are the UK lines captured on 15 October 2026. There was no lab test, and the score does not name the most accurate hygrometer in the United Kingdom. The four weights below sum to 100.
Amazon stars, damped by review count
35%Star points start from the amazon.co.uk rating, then a smaller file is damped. A count of 135 is not treated like a count of 1,916.
Listing clarity
30%Points come off when two lines on the same card cannot both be the product: a battery line against a voltage line, a temperature bullet against the attribute, two accuracy lines, or a German-only note on a UK listing.
Shelf price
15%The cheapest captured price scores highest. This set runs from about £9.71 to £17.96, so a £17 dial is not scored as if it were a data logger.
Job fit from UK review notes
20%A clear indoor or indoor-outdoor job, a large UK sample, and a printed regeneration interval add points. A rattle, a stuck needle, or a file too small to lean on takes points off. Non-UK review text is not treated as UK opinion.
Choose the job before the metal ring or the Germany line. A no-battery indoor dial, a named synthetic-hair movement, and a bullet that says indoor and outdoor are different buys. That order is set out in the [TFA Dostmann hygrometer buying guide](/hub/climate-measuring/tfa-dostmann-hygrometer/sub/tfa-dostmann-hygrometer-buying-guide).
A TFA Dostmann hygrometer in this set is an analogue thermo-hygrometer. One dial shows relative humidity and temperature, usually with coloured comfort bands. It does not measure water in plaster, and it does not repair a building. There is no dew point, no 24-hour trace, and no alarm. The Mould Radar sits outside this set. Do not treat any of these dials as accurate to 1% relative humidity, and do not apply a ±3% RH tolerance to them.
The Centre for Sustainable Energy aim, and the comfort band printed on several bullets, is not a statute. GOV.UK gives no single percentage. A reading of 50% RH does not prove a dry wall, and the dial does not show that a landlord is in breach.
A damp cloth is not a reference, and 100% from the cloth is not the target. TFA’s cloth step is a warm tea towel that does not drip. Adjust later, beside a reference, after 30–45 minutes. Do not use this method on an electronic TFA meter.
The 45.2045.02 country-of-origin line is China, and its bullets do not say Germany. Do not hang an indoor metal-ring model in a greenhouse. The 45.2027 scale is the German version, so do not read those words as English labels.
Start with the job, not the metal ring. A no-battery indoor dial, the words synthetic-hair on TFA’s English page, and a bullet that says indoor and outdoor are three different buys. TFA builds two analogue movements: a synthetic-hair fibre, and a spring with a coated bimetallic coil. English pages for the 45.2027 and the 45.2043 say synthetic-hair. The amazon.co.uk bullet on the 45.2043.51 says it as well.
TFA’s English manual says to regenerate an analogue movement at least every six months. Wrap the dial in a warm tea towel wrung until it does not drip, for about 15–30 minutes. The pointer should then sit about 90–99% RH. The FAQ puts the same step at about 15 minutes and about 95–99% RH. A damp cloth is not a reference. Adjust later, in room air beside a reference, after 30–45 minutes, with the rear cross-head screw.
Three typical situations, each with a recommendation from this comparison.
You want an indoor dial for a house, basement, or garage, and you will pay about £17.39 because TFA’s English page says synthetic-hair. The amazon.co.uk title is the German version, and the listing does not name that sensor.
You need the only listing in this set that says indoor and outdoor. It is about £9.71, with regeneration printed as every 6 months. The country of origin is China, and the temperature line is ±2 °C.
You want the small metal-ring indoor dial with 4.1 from 3,045 reviews, at about £10.94. The battery attribute says cells are required and names no type, while UK reviews in the sample describe no cell.
The top pick for an indoor dial is the TFA 45.2027 at about £17.39, with 4.2 from 1,916 amazon.co.uk reviews, when a German scale is acceptable and TFA’s English page is why you are paying for synthetic-hair. It is not a lab result. The best value is the TFA 45.2045.02 at about £9.71, with 4.2 from 1,248 reviews, when you need the only listing that says indoor and outdoor. Its country of origin is China. The 45.2024 is the small metal-ring dial with the largest review file, 4.1 from 3,045, if you can live with a battery line that does not match those UK reviews.
TFA 45.2027 indoor hygrometer
Indoor dial at about £17.39, 4.2 from 1,916 reviews, when a German scale is acceptable and TFA’s English page says synthetic-hair.
TFA 45.2045.02 indoor-outdoor hygrometer
Lowest captured price at about £9.71, 4.2 from 1,248 reviews, when the listing’s job is indoor and outdoor.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Manufacturer and public UK sources used for this comparison. Listing prices, stars, and review counts are from amazon.co.uk on 15 October 2026.
Expert source (DIY & tools): Charlie White (Charlie DIYte) (external profile) – public expert commentary used as a research source, not as a contributor to our pages.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars, and review counts are the UK listing lines captured on 15 October 2026. We did not run a lab test.
