Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.
Q: I just created an inch to mm conversion calculator and I am writing a blog post announcing its launch. When should I capitalize the terms inch and millimeter? Does it matter if I'm spelling it out? What if I'm using an abbreviation or symbol? What if it begins a sentence?.
A: 
No, units generally do not need capitalization when spelled out. For SI units, the Bureau International des Poids et Mesures is the authority: Unit names are normally printed in roman (upright) type, and they are treated like ordinary nouns. In English, the names of units start with a lower-case letter (even when the symbol for the unit begins with a capital letter), except at the beginning of a sentence or in capitalized material such as a title. In keeping with this rule, the correct spelling of the name of the unit with the symbol C is 'degree Celsius' (the unit degree begins with a lower-case d and the modifier Celsius begins with an upper-case C because it is a proper name). The International System of Units (SI), 8th ed., Sec.5.2 However, capitalization is used in the following cases: Symbols for SI units named after people, for example: 1 ampere, abbreviated as 1 A 1angstrom or 1angstrom, abbreviated as 1A Note that the names of the units themselves are lowercase. The symbol for litre or liter is l, but is often written as L to prevent it from looking like the digit 1. It is also sometimes rendered in lowercase cursive form for the same reason: The litre, and the symbol lower-case l, were adopted by the CIPM in 1879 (PV, 1879, 41). The alternative symbol, capital L, was adopted by the 16th CGPM (1979, Resolution 6; CR, 101 and Metrologia, 1980, 16, 56-57) in order to avoid the risk of confusion between the letter l (el) and the numeral 1 (one). The International System of Units (SI), 8th ed., Sec.4.1 Temperature degree units, e.g. degrees Celsius or degrees Fahrenheit, abbreviated as C and F, as stated in the quote above. Note, however, that the kelvin follows the rule for units named after people: 1kelvin, abbreviated as 1K. Special non-SI units, such as the British thermal unit, abbreviated BTU or Btu, or the US gallon, for obvious reasons. The astronomical unit is abbreviated either as au or AU. The international unit is abbreviated IU. A byte is abbreviated as B; a bit is abbreviated as b. A decibel is abbreviated as dB. One unit where capitalization makes a huge difference is the calorie. A calorie (abbreviated cal) is the energy needed to heat one gram of water by 1C. This unit is used by physicists and chemists. A Calorie (abbreviated Cal or kcal) is actually a kilocalorie 1000 times the amount of energy of a calorie. This unit is used by dieticians and the general public when describing food. Naturally, at the beginning of a sentence, the usual rule that the first letter be capitalized overrides all of the above. For example, Watt for watt, a RISC chip delivers better performance than a CISC chip. Also note that capitalization is significant in the SI prefixes. For example, mW is a milliwatt, and MW is a megawatt.