How this instrument works
The litre began as a French Revolutionary convenience — a cubic decimetre of liquid, named in 1795 and never quite promoted to full SI rank. It remains an outsider, accepted for use alongside SI units while the coherent unit of volume stays the cubic metre. It also drifted once. From 1901 the 3rd CGPM tied the litre not to geometry but to the volume occupied by one kilogram of pure water at its density maximum, a quantity later measured at 1.000028 dm³. That definition was abolished in 1964, when the 12th CGPM handed the name back to the cubic decimetre, exactly.
A centilitre needs no separate definition at all. Centi- is an SI prefix meaning precisely one hundredth, part of the original decimal ladder of 1795, so a centilitre is one hundredth of a litre by construction: 10 millilitres, 10 cubic centimetres, roughly two thirds of an American tablespoon. That is why this factor reads 100.0 rather than 99.997-something. Nothing was weighed or poured to obtain it. Shift the decimal point two places right and the job is done, whether your figure is 0.05 l of vanilla extract or 2 l of stock.
Which unit you meet depends on where you shop. Centilitres dominate drink labelling across continental Europe: still wine at 75 cl, spirits at 70 cl, beer in 33 cl and 50 cl formats — nominal sizes fixed for that market by Directive 2007/45/EC. The International Bartenders Association writes official specifications the same way, so a Negroni is 3 cl gin, 3 cl Campari and 3 cl sweet vermouth rather than an ounce of each. Cross the Atlantic and this unit nearly vanishes: American kitchens, labels and laboratories reach for millilitres or fluid ounces, and NIST guidance steers writers toward prefixes that step in thousands, leaving centi- almost entirely to the centimetre.
- Type your volume into the Litres (l) field; it opens at 2 l, the size of a household soda bottle.
- Read the answer from the Centilitres (cl) field, which recomputes on every keystroke.
- Working backwards from a label instead? Divide that figure by 100 before typing — 70 cl of gin goes in as 0.7.
- Need millilitres? Multiply the Centilitres (cl) result by 10, since one centilitre is 10 mL exactly.
Worked example — batching two litres of Negroni
You have a 2-litre jug and a recipe specified in centilitres. Enter 2 in the Litres (l) field and the Centilitres (cl) field answers 200.0. At 3 cl of each of three ingredients, one drink takes 9 cl, so your jug yields 22 servings with 2 cl to spare — meaning 66 cl drawn from each bottle, which a single 70 cl gin covers.
That same 200 also explains a supermarket shelf. Six 33 cl cans total 198 cl, two centilitres shy of the 2 l bottle standing beside them, and a 75 cl wine bottle is three quarters of it. Because this step is nothing but a decimal-point move, both directions stay exact: 200 divided back by 100 returns 2 l with nothing left over.
Questions
Is one litre exactly 100 centilitres?
Yes, exactly — that relation is definitional rather than measured. Centi- is the SI prefix for one hundredth, so a centilitre is one hundredth of a litre by construction and the multiplier 100 carries no uncertainty whatsoever. One historical asterisk: between 1901 and 1964 the litre was pinned to the volume of a kilogram of water instead of a cubic decimetre, and that older litre ran about 28 parts per million larger. Even then the prefix held — 100 of those centilitres still made one of those litres.
What is the difference between centilitres and millilitres?
One centilitre is 10 millilitres, exactly; cl sits a single decimal place above mL. The slip worth guarding against is a factor-of-ten error when copying from packaging: a 70 cl spirits bottle holds 700 mL, not 70 mL, and a 5 cl measure in a bar book means 50 mL. Decilitres sit one place the other way, so 1 dl is 10 cl — Scandinavian recipes lean on dl where French and Italian ones reach for cl.
Why are wine bottles 75 cl rather than a round litre?
Because permitted sizes are legislated, not natural. Directive 2007/45/EC lists the nominal quantities allowed for wine and spirits sold across the EU, and 75 cl for still wine and 70 cl for spirits are what survived that tidy-up; Great Britain kept both figures after leaving. Expressed in litres they are 0.75 and 0.7, which this sheet will show if you enter them. Those numbers look awkward only because the trade counts in centilitres and the shelf edge does not.
Should the symbol be written cl or cL?
Both are correct. The 16th CGPM accepted a capital L as an alternative symbol for the litre in 1979, precisely because a lowercase l is easy to mistake for the digit 1 in many typefaces. Neither form takes a plural s or a full stop: 70 cl, never 70 cls. What has no official standing is the script ℓ that still turns up on packaging — BIPM and NIST list only l and L. This page prints the lowercase form to match its field labels.
Does temperature or the liquid affect the result?
Not the conversion itself. The multiplier relates two units of volume, so it applies to mercury, milk and liquid hydrogen alike, and nothing about it shifts with temperature. What does shift is the liquid: warm water from 4 °C to 60 °C and it swells by roughly 1.7%, while the glass measuring it expands too. Trade and laboratory glassware is normally calibrated at 20 °C for that reason, and the same 1964 CGPM resolution advised against using the litre at all where the highest precision matters.
How do I convert centilitres back to litres by hand?
Divide by 100 — shift the decimal point two places left. A 33 cl can becomes 0.33 l, a 70 cl bottle 0.7 l, and 250 cl is 2.5 l. Since the multiplier is exact, the return trip loses nothing at all: any quantity you push through both directions arrives at the number you started with, give or take whatever digits your display chooses to show.