Convert dm to cm decimetres ↔ centimetres Free Online Secure
Type a value in decimetres and read it in centimetres at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert dm to cm (decimetres ↔ centimetres)
| dm | cm |
|---|---|
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 5 | 50 |
| 10 | 100 |
| 20 | 200 |
| 50 | 500 |
| 100 | 1000 |
Where these units come from
The metre was first defined in 1793 as a ten-millionth of the distance from the equator to the North Pole — a definition nobody could check without surveying a quarter of the planet. It has been redefined four times since, each time to something steadier: a platinum bar, then a prototype kept in Paris, then a wavelength of krypton light, and since 1983 the distance light travels in vacuum in 1/299,792,458 of a second. The inch stopped being a separate thing in 1959, when six countries agreed to define it as exactly 25.4 mm. That agreement is why every conversion on this page between a metric and an imperial length is exact rather than measured: both sides now descend from the same definition.
Where you meet them
Millimetres are the working unit of engineering drawings and of anything made in a workshop; centimetres belong to tailoring, furniture and school rulers; metres to rooms, fabric and running tracks. Feet and inches survive in aviation altitudes worldwide, in American and British construction, and in the diagonal of every screen you have ever bought. Nautical miles are not a quaint survival — one is a minute of latitude, which is why ships and aircraft still navigate in them.
Questions people ask
Does anyone still use decimetres?
Rarely on its own: a decimetre is ten centimetres, and most people jump straight from centimetres to metres. It survives in school lessons and in one important place, the litre, which is exactly one cubic decimetre. That is why a litre of liquid fits in a cube ten centimetres on each side.
Where is the centimetre used in everyday life?
For anything a person measures against their own body: height, clothing sizes, the length of a sleeve, the width of a shelf, the dimensions of a parcel. A centimetre is roughly the width of a fingernail, which makes it easy to picture. It is large enough to avoid long strings of digits and small enough that you rarely need a decimal.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
From a school exercise to a workshop plan: how to convert dm to cm
The decimetre is a unit that many adults have not used since school, yet it is exactly the unit in which a surprising number of plans, recipes for aquariums and children's textbooks are written. A Dutch carpenter speaks of a plank of "vier decimeter", a Belgian teacher sets a worksheet in decimetres and a hobbyist reading a foreign magazine meets "dm" on a diagram without explanation. To read such a figure on an ordinary ruler, you have to convert dm to cm. This page does it on the spot: enter a length in decimetres and read it in centimetres.
The conversion is a multiplication by ten, so it is exact and simple, but it is also easy to do in the wrong direction when the unit is unfamiliar. People who rarely meet decimetres are unsure whether the number should grow or shrink. The sections below explain the rule, give worked examples, introduce both units, compare them, list the places the conversion shows up and warn about the usual mistakes.
The rule for convert dm to cm
Multiply by ten
A decimetre is a tenth of a metre, and a centimetre is a hundredth, so one decimetre is exactly ten centimetres. To convert dm to cm, multiply the number by ten, which is the same as moving the decimal point one place to the right. 4 dm is 40 cm; 2.5 dm is 25 cm; 0.6 dm is 6 cm; 12.75 dm is 127.5 cm. The result is exact, because both units are defined from the metre by powers of ten.
Worked examples
A school desk 6 dm wide is 60 cm wide. A bookshelf 18 dm long is 180 cm. A baby 5 dm long at birth is 50 cm. A shoe 2.8 dm in length is 28 cm. In each case the digits stay the same and a zero or a shifted point appears at the end.
Mentally
Think of a decimetre as a hand span, about ten centimetres: three hands is thirty centimetres, ten hands a metre. If the answer is not ten times the starting number, you have divided by mistake.
Keeping track of digits
A length given as 2.5 dm is 25 cm, not 25.0 cm. Keep the number of significant digits of the original. If a plan says 12 dm, then 120 cm is enough, not 120.00.
The decimetre
A tenth of a metre
The decimetre is a tenth of a metre, from the Latin decimus. It is about the width of an adult hand, four inches in imperial terms. It was one of the original units of the metric system in the 1790s, and its main claim to fame is that a cube one decimetre on a side holds a litre.
Where it appears
Dutch and Belgian schools, some Eastern European textbooks, and the area and volume units dm² and dm³. The symbol is dm. Outside these regions, it appears in science and in some craft patterns.
The centimetre
A hundredth of a metre
The centimetre is the unit of most household measurements worldwide: height, furniture, fabric, shoes, book sizes. A centimetre is roughly the width of a fingernail. The prefix centi means a hundredth. The symbol is cm.
Where it appears
Rulers, tape measures, tailoring patterns, growth charts and shop labels. In most countries it is the first metric unit children learn to measure with.
Decimetre and centimetre compared
One decimetre is ten centimetres, so a length in centimetres has one more digit than the same length in decimetres. A person of 17 dm is 170 cm. In practice, the centimetre is the more familiar unit and the decimetre the more convenient one for calculation of volume.
If you are writing for a general audience, use centimetres; if the context is a textbook on the metric system or a volume calculation in litres, decimetres are the natural choice. Whichever you choose, state the unit clearly to avoid a mistake of a factor of ten.
Where people need to convert dm to cm
Foreign textbooks and worksheets
Parents helping a child with homework from a Dutch, Belgian or Eastern European school may find a question such as: "A rope is 12 dm long. How many centimetres is that?" The expected answer is 120 cm. The same worksheets ask for conversions in both directions, and an adult who can convert dm to cm quickly can check the answers without a lesson in the metric system.
Aquariums and fish tanks
Fish tank sizes are often quoted in decimetres in the Netherlands and Germany. A tank 6 dm × 3 dm × 4 dm is 60 cm × 30 cm × 40 cm and holds 72 litres. Because a litre is one cubic decimetre, the decimetre route is the easiest way to know the capacity. Convert to centimetres when you must compare with the shop's catalogue, which uses the larger numbers.
Sewing and knitting
Some patterns give gauge in stitches per decimetre. If a pattern says 25 stitches per 10 cm, that is 25 per decimetre; a sleeve of 5 dm is 50 cm. Knitters who swap between metric and imperial patterns learn to convert both ways.
Maps, models and kids' crafts
Model railways, doll's houses and school projects use decimetres to keep numbers small: a model 2.5 dm long is 25 cm, and at a scale of 1:10 it represents 2.5 m. In classrooms, the decimetre is the base of the "metre ladder" taught to young pupils.
A quick history of tens
Why the metric system uses powers of ten
Before the 1790s, units were based on body parts and local custom, and fractions such as twelfths and sixteenths were common. French reformers insisted on decimal division so that any child could do the arithmetic. They gave the new units simple names, with prefixes from Latin for fractions and Greek for multiples. The decimetre came out of that scheme, along with the centimetre and the millimetre.
The fate of the decimetre
Over time, practice favoured the metre, the centimetre and the millimetre, which suit most tasks, while the decimetre faded. It survived in education because it makes the connection between length, area and volume visible, and in the unit of capacity, the litre. When you convert dm to cm you step on that rung of the ladder.
Why the extra zero matters
Counting in the shop
When you convert dm to cm for a purchase, the extra zero is not a detail. A shelf listed as 18 dm and ordered as 18 cm would be an eighth of a metre long, a toy rather than furniture. Retailers see such returns every week, and most could be avoided by writing the unit next to every number and reading it aloud once before paying. If a figure looks too small or too large for the object, stop and check the unit. A sofa of 20 dm is a normal three-seater; one of 20 cm is a cushion.
Checking by comparison
Hold up your hand for a decimetre, your forearm for three or four, and your arm span for about seventeen. Compare the object with these anchors before you finalise the order. The habit takes a minute and protects you from the slip that costs the most: a correct calculation applied to the wrong unit.
Volume, area and the litre
Square and cubic decimetres
A square decimetre is 100 square centimetres; a cubic decimetre is 1,000 cubic centimetres, which is exactly one litre. If a container is 3 dm × 2 dm × 2 dm, its capacity is 12 litres. In centimetres, the same container is 30 × 20 × 20, giving 12,000 cm³. Convert to the unit that gives the simpler arithmetic.
Practical capacity checks
A fridge drawer of 4 dm × 3 dm × 2 dm holds 24 litres. A cat litter tray of 5 dm × 4 dm holds a few litres at a depth of 1 dm. Keep the unit consistent: do not multiply dm by cm.
Reading old plans
Decimetres on drawings
Technical drawings from some countries and eras use decimetres for medium-length dimensions. A cabinet drawing may say 9 and 14 dm for width and height. Look for a note of units in the corner, and convert dm to cm before ordering material. If no note exists, check against a dimension that you know, such as a door height of about 20 dm.
Estimating by eye
Hold your hand flat with fingers together: that is about a decimetre. A pen is 1.5 dm, a shoebox 3 dm, a loaf of bread 4 dm. These everyday objects give you a sense of scale to check a conversion.
The decimetre and the body
Growth charts and clothing
A newborn averages 5 dm, a one-year-old 7.5 dm, an adult 16 to 18 dm. Paediatric growth charts in some countries mark length in decimetres on one axis and centimetres on another, which is why you may need to convert dm to cm to compare with a standard chart. Child sizes in clothes are sometimes in decimetres of height.
Sport
A high jump bar at 20 dm is two metres; a long jump of 85 dm is 8.5 m. Athletics rarely uses decimetres, but sports reports in some languages mix them with metres and centimetres.
Mixed units in one problem
Adding dm and cm
To add 3 dm and 25 cm, convert 3 dm to 30 cm, then add: 55 cm. Alternatively, convert 25 cm to 2.5 dm and add: 5.5 dm. Both are the same length. Pick one unit and stay with it through the sum.
Subtracting and comparing
To compare 12 dm and 130 cm, change 12 dm to 120 cm; 130 cm is longer by 10 cm. Comparisons are the commonest reason to convert dm to cm, as when a shelf must fit in a gap.
Tools and technology
Rulers and apps
Some school rulers show decimetres with a bold line every ten centimetres. Measurement apps on phones can switch between units. Laser measures can show a result in a unit you select. If you work often with decimetres, set your tool to centimetres and mentally convert dm to cm only for the final report.
Spreadsheets
In a spreadsheet, put the unit in the header of each column and use a formula such as =A2*10. Never type numbers with units into cells; keep units in labels. This habit prevents most errors in lists of dimensions.
Teaching tips
Use the hand
Children learn the decimetre best through the hand span: ten hands make a metre, and each hand is ten centimetres. Let them measure the classroom with a decimetre strip and write the results in both units. Ask them to guess before they measure, and discuss the differences.
Games
Play "closer to a decimetre": place objects on a table and ask whether each is longer or shorter than ten centimetres. Then convert dm to cm for the guesses that were far away. Mistakes of a factor of ten make memorable lessons.
A worked project: a shelf in decimetres
Planning in the unit of the plan
Imagine you have found a plan for a children's bookcase on a Dutch hobby site. It lists the sides at 9 dm, the shelves at 4.5 dm wide and 2.2 dm deep, and the gaps between shelves at 2.4 dm. You want to buy boards at a shop that cuts in centimetres. The first step is to convert dm to cm for every figure: the sides become 90 cm, the shelves 45 cm by 22 cm, and the gaps 24 cm. Write the new list beside the old one and check one figure the other way round before you order.
Checking the total height
With four shelves and three gaps between them, the inner height is 3 × 24 = 72 cm plus the thickness of the boards. If the boards are 1.8 cm thick, the total is 72 + 4 × 1.8 = 79.2 cm, which is close to the 90 cm sides once you add a base and a top. Doing the sum in centimetres, after the conversion, prevents a decimal slip from turning a bookcase into a skyscraper.
Looking after your numbers
Write down both
When you convert a measurement that you will use again, write down both versions with their units. A note in a notebook such as "table 12 dm = 120 cm" saves you from repeating the sum in a shop with bad reception. If you work in a team, share the same version, and state which unit is the source. Disputes about a centimetre are common when two people use different rulers.
Test on a known object
Before trusting a rule on an unfamiliar unit, test it on something you know. A sheet of A4 paper is 2.97 dm long, which is 29.7 cm; if your result is 2.97 cm or 297 cm, something is off. A door is about 20 dm high, 200 cm. Checking against a familiar object is the quickest way to catch a slip.
Be patient with the unfamiliar
People who rarely use decimetres often feel uneasy about the unit. The cure is a few minutes of practice with objects at hand: measure a pen, a book and a phone in centimetres, then divide by ten to read them in decimetres. After three or four examples the unit stops feeling strange. When you next convert dm to cm, the decimal point will move without hesitation.
More values for convert dm to cm
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 dm = 1 cm
- 0.5 dm = 5 cm
- 3 dm = 30 cm
- 4 dm = 40 cm
- 7 dm = 70 cm
- 15 dm = 150 cm
- 20 dm = 200 cm
- 75 dm = 750 cm
- 200 dm = 2,000 cm
- 500 dm = 5,000 cm
- 2,000 dm = 20,000 cm
- 10,000 dm = 100,000 cm
Mistakes when you convert dm to cm
Dividing instead of multiplying
Going from the larger unit to the smaller means a bigger number. Dividing by ten is the conversion the other way round.
Mixing up dm and mm
One decimetre is 100 millimetres, not 10. If you need millimetres, use the dm to mm page or multiply by a hundred.
Forgetting the unit
A bare "12" could be 12 dm or 12 cm. Always write the unit with the figure.
Quick answers
How many centimetres are in a decimetre?
Ten.
How do I convert dm to cm?
Multiply by ten, or move the decimal point one place to the right.
What is 8 dm in cm?
80 cm.
Is the conversion exact?
Yes, exactly.
Is my number sent anywhere?
No. The calculation runs in your browser.
Related pages and a last word
If you work with these units, the following conversions are close by: Convert dm to ft, Convert dm to km, Convert in to cm, Convert m to cm, Convert cm to mm, Convert °C to °F, Convert °F to °C, Convert L to gal, Convert gal to L. The reverse of this page is Convert cm to dm.
In short, to convert dm to cm multiply by ten, check that the answer is ten times larger and keep the digits your measurement supports. Your number stays on your device: nothing is uploaded, and there is no account.