Was ist ein/eine Centimeter (cm)?
Formal Definition
The centimeter (symbol: cm) is a unit of length in the International System of Units (SI) equal to one hundredth of a meter (10⁻² m). The prefix "centi-" derives from the Latin "centum," meaning one hundred. One centimeter equals 10 millimeters, and 100 centimeters make up one meter. It is one of the most commonly used units for measuring everyday objects and human body dimensions.
Practical Scale
The centimeter occupies a uniquely useful position in the range of metric length units. It is large enough to measure objects by eye and small enough to provide reasonable precision for everyday tasks. The width of an adult fingernail is approximately 1 cm, a standard pencil is about 19 cm long, and a sheet of A4 paper measures 21.0 × 29.7 cm. This human-scale familiarity makes the centimeter the most frequently used metric length unit in daily life.
CGS System
Historically, the centimeter served as the base unit of length in the centimeter-gram-second (CGS) system of units, which was widely used in science from the 1830s until the SI system replaced it in 1960. Many scientific formulas and constants were originally expressed in CGS units, and some fields — particularly astrophysics and electromagnetism — continued to use CGS well into the 21st century.
Etymology
Latin Roots
The word "centimeter" combines the Latin prefix "centum" (one hundred) with the Greek-derived "meter" (from "metron," meaning measure). The French form "centimètre" was coined in the 1790s as part of the metric system. The creators of the metric system used Latin-derived prefixes for submultiples (centi-, milli-, deci-) and Greek-derived prefixes for multiples (kilo-, hecto-, deca-).
Spelling Variations
American English uses "centimeter" while British English uses "centimetre." Both spellings are recognized internationally. The abbreviation "cm" is universal and unchanged across all languages and writing systems. The International Bureau of Weights and Measures (BIPM) uses the French spelling "centimètre" in its official publications.
Historical Context
The centimeter gained particular prominence when the CGS system of units was established in 1832 by Carl Friedrich Gauss. Gauss proposed using the centimeter, gram, and second as the three fundamental units for scientific measurement. This system dominated physics for over a century and shaped the way generations of scientists thought about measurement.
Precise Definition
SI Definition
The centimeter is defined as exactly one hundredth of a meter: 1 cm = 0.01 m = 10⁻² m. Since the meter is defined as the distance light travels in vacuum in 1/299,792,458 of a second, one centimeter is the distance light travels in vacuum in approximately 33.356 picoseconds (3.3356 × 10⁻¹¹ seconds).
Practical Realization
Centimeter-scale measurements are typically made using rulers, calipers, and coordinate measuring machines (CMMs). High-quality machinist's calipers can measure to 0.01 mm (0.001 cm) precision, while CMMs achieve micrometer-level accuracy. For industrial applications, laser interferometers provide nanometer-level precision over centimeter and meter ranges.
Traceability
All centimeter measurements are traceable to the SI definition of the meter through calibrated measurement instruments. National metrology institutes maintain standards for length calibration, including gauge blocks (also called Johansson gauges or Jo blocks) that provide precise reference lengths from millimeters to hundreds of millimeters with uncertainties of less than 0.1 micrometers.
Geschichte
Birth in the Metric System
The centimeter was introduced as part of the original metric system established during the French Revolution. When the meter was defined in 1791 as one ten-millionth of the distance from the North Pole to the Equator, the centimeter was automatically defined as one hundredth of that distance. The first practical use of the centimeter was in French commerce and education following the adoption of the metric system by law on 10 December 1799.
The CGS System
In 1832, Carl Friedrich Gauss proposed a system of absolute units for measuring magnetic phenomena, based on the centimeter, gram, and second. This centimeter-gram-second (CGS) system was formally adopted by the British Association for the Advancement of Science in 1874. For nearly a century, the CGS system was the standard for scientific measurement, and many fundamental relationships in physics were expressed in CGS units. The dyne (force), erg (energy), and barye (pressure) were CGS-derived units based on the centimeter.
Transition to SI
In 1960, the 11th General Conference on Weights and Measures (CGPM) established the International System of Units (SI), which replaced the CGS system with the meter-kilogram-second (MKS) system as the basis for scientific measurement. The centimeter lost its status as a base unit but remained widely used in everyday measurement. Some scientific fields, particularly astrophysics, continued using CGS units for decades. Even today, CGS-Gaussian units appear in some physics textbooks and research papers.
Global Adoption
As the metric system spread worldwide through the 19th and 20th centuries, the centimeter became the most commonly used unit for measuring everyday lengths in metric countries. Body height, clothing sizes, screen sizes (in many countries), and room dimensions are commonly expressed in centimeters. The centimeter's status as the most intuitive metric length unit for human-scale objects has made it indispensable.
The Centimeter in Engineering
In engineering and manufacturing, the millimeter gradually replaced the centimeter as the preferred unit during the 20th century. Engineering drawings and technical specifications in most countries now use millimeters rather than centimeters, because millimeters allow integer dimensions for most components, reducing the need for decimal points and the errors they can introduce. This convention is particularly strong in mechanical engineering, architecture, and construction in metric countries.
Aktuelle Verwendung
In Daily Life
The centimeter is one of the most frequently encountered units of measurement in daily life across metric countries. Body height is universally expressed in centimeters (or meters and centimeters) outside the US and UK — a person might be described as 175 cm tall. Clothing sizes in Europe and Asia are based on body measurements in centimeters: chest, waist, hip, and inseam measurements are all in centimeters.
In Medicine
In medicine, the centimeter is the standard unit for many clinical measurements. Newborn length (typically 48 to 52 cm), wound dimensions, tumor sizes, and organ measurements are all expressed in centimeters. Pediatric growth charts track height in centimeters. In radiology, the sizes of lesions, nodules, and anatomical structures are measured in centimeters and millimeters. Surgical incision lengths are planned and documented in centimeters.
In Science and Education
In science education, the centimeter is usually the first unit of length that students learn to use with a ruler. Laboratory measurements of small objects, liquid levels in graduated cylinders, and plant growth in biology experiments are commonly expressed in centimeters. The centimeter cube (cm³, also written cc or mL) is a fundamental unit of volume equal to one milliliter.
In Technology
Screen sizes for televisions and monitors are expressed in centimeters in many countries (though inches dominate globally for this specific measurement). Paper sizes in the ISO 216 standard (A4, A3, etc.) are defined in millimeters but commonly discussed in centimeters. In interior design, furniture dimensions are given in centimeters throughout most of the world.
Everyday Use
Measuring People
The centimeter is the standard unit for measuring human height in most countries. When someone says they are 180 cm tall, this is immediately understood across Europe, Asia, Africa, and South America. Babies' lengths are tracked in centimeters from birth, and growth charts at pediatric clinics use centimeters. Passports in most countries list height in centimeters. Body measurements for tailored clothing — chest, waist, hips, sleeve length, inseam — are all taken in centimeters.
Home and Furniture
In the home, centimeters are used for measuring furniture, room dimensions, and decorating projects. A standard doorway is about 200 cm tall and 80 cm wide. Kitchen countertops are typically 85 to 90 cm high. When buying curtains, shelves, or picture frames, measurements are in centimeters. DIY projects from assembling IKEA furniture to hanging artwork require a tape measure marked in centimeters.
School and Office
Students worldwide use centimeter-marked rulers for drawing, geometry, and science. Standard school rulers are typically 30 cm long. Graph paper in metric countries uses 1 cm or 0.5 cm grids. Paper sizes are commonly discussed in centimeters: A4 paper is 21 × 29.7 cm, and letter paper is about 21.6 × 27.9 cm.
Crafts and Sewing
In sewing, knitting, and crafts, the centimeter is indispensable. Fabric is sold by the meter but pattern pieces are measured in centimeters. Seam allowances of 1 or 1.5 cm are standard. Knitting and crochet gauge swatches are measured in centimeters per stitch count. Quilting patterns specify piece dimensions in centimeters in metric countries.
In Science & Industry
The CGS Legacy
The centimeter's most significant scientific role was as the base unit of length in the CGS system. In this system, force was measured in dynes (1 dyne = 1 g·cm/s²), energy in ergs (1 erg = 1 g·cm²/s²), and pressure in baryes (1 barye = 1 g/(cm·s²)). Although SI has largely replaced CGS, some CGS units persist in specialized fields. Astronomers use the CGS system extensively, expressing luminosity in ergs per second and magnetic field strength in gauss (a CGS unit).
Spectroscopy
In spectroscopy, the wavenumber — the number of wave cycles per centimeter (cm⁻¹) — is a standard unit for expressing the frequency of electromagnetic radiation, particularly infrared radiation. A wavenumber of 1000 cm⁻¹ means 1000 complete wave cycles fit within one centimeter. This unit is preferred over frequency in hertz because it is directly proportional to energy and inversely proportional to wavelength, making it convenient for identifying molecular vibrations.
Volume and Density
The cubic centimeter (cm³) is a fundamental unit of volume equal to exactly one milliliter (mL). This equivalence is widely used in chemistry, medicine, and engineering. In medicine, dosages and fluid volumes are often expressed in mL (= cm³). Density is commonly expressed in grams per cubic centimeter (g/cm³) — water has a density of approximately 1.0 g/cm³, iron about 7.87 g/cm³, and gold about 19.3 g/cm³.
Biology and Microscopy
In biology, the centimeter is used for measuring organisms and anatomical structures at the macroscopic scale. Cell biology typically uses micrometers, but tissue samples, organ dimensions, and whole-organism measurements use centimeters. Histological sections are prepared from tissue blocks measured in centimeters, and pathology reports describe specimen dimensions in centimeters.
Multiples & Submultiples
| Name | Symbol | Factor |
|---|---|---|
| Nanometer | nm | 10⁻⁹ m |
| Micrometer | μm | 10⁻⁶ m |
| Millimeter | mm | 10⁻³ m |
| Centimeter | cm | 10⁻² m |
| Decimeter | dm | 10⁻¹ m |
| Meter | m | 10⁰ m |
| Kilometer | km | 10³ m |
Interesting Facts
The centimeter was the base unit of length in the CGS system used in science for over 125 years (1832-1960). Many fundamental physics equations were originally written in CGS units, and some fields like astrophysics still prefer them.
One cubic centimeter (cm³) is exactly equal to one milliliter (mL). This elegant relationship was designed into the metric system: the original kilogram was defined as the mass of 1000 cm³ of water.
The wavelength of visible light ranges from about 0.000038 cm (violet) to about 0.000075 cm (red). This means roughly 13,000 to 26,000 wavelengths of light fit within a single centimeter.
A standard credit card is 8.56 cm × 5.398 cm, a dimension standardized by ISO/IEC 7810. This size was chosen to fit comfortably in wallets and card readers worldwide.
Human hair grows at approximately 1.25 cm per month, or about 15 cm per year. This rate is remarkably consistent across individuals, though it varies slightly by age and ethnicity.
The tallest person in recorded history, Robert Wadlow, measured 272 cm (8 feet 11.1 inches) at his peak. The shortest adult ever recorded, Chandra Bahadur Dangi, was 54.6 cm (21.5 inches) tall.
A4 paper (21.0 × 29.7 cm) is designed so that its aspect ratio is 1:√2. This means folding it in half creates a sheet with the same proportions — an elegant mathematical property.
In the CGS system, the speed of light is approximately 3 × 10¹⁰ cm/s. This number was so commonly used in physics that it was simply memorized as "three times ten to the tenth."
The diameter of a human red blood cell is about 0.0007 cm (7 micrometers). About 1,400 red blood cells lined up side by side would span one centimeter.
Regional Variations
Metric Countries
In the vast majority of countries, the centimeter is used extensively in daily life. Europeans, Asians, South Americans, and Africans measure height in centimeters, buy clothing sized in centimeters, and use centimeter-marked rulers and tape measures. The centimeter is so fundamental to daily measurement in these countries that it requires no explanation or context.
The United States
In the United States, the centimeter is not commonly used in daily life, where inches dominate for similar measurements. However, Americans encounter centimeters in science classes, medical settings (where tumor sizes and wound measurements use centimeters), and when dealing with metric products. Some American rulers include both inches and centimeters. The centimeter is gaining visibility as global products increasingly use metric dimensions.
Engineering Conventions
A notable regional variation exists in engineering: many countries that use centimeters in daily life use millimeters exclusively in engineering and construction drawings. Germany, Japan, and most of Europe specify all technical dimensions in millimeters, not centimeters. This means a dimension of 2.5 cm would be written as 25 mm on an engineering drawing. The United States, however, uses inches and fractions of inches (or decimal inches) in many engineering contexts.