How this instrument works
A cubic centimetre is a cube one centimetre on each edge, identical in volume to one millilitre since the litre was redefined as exactly one cubic decimetre in 1964. The US fluid ounce descends from a completely different lineage: Queen Anne's 1707 statute fixed the English wine gallon at 231 cubic inches, America kept that vessel after independence while Britain later abandoned it, and dividing that gallon into 128 equal parts gives one fluid ounce of 29.5735295625 millilitres, exact once the inch itself was pinned to 25.4 mm in 1959.
Because both units are exact by definition, the factor connecting them — 0.0338140227018 — is a rounded display of an endless repeating fraction rather than a rounded measurement; reversing the conversion by multiplying an ounce figure by 29.5735295625 returns the original cubic centimetre value with nothing lost. Only the digits shown on screen are ever approximate, never the relationship itself.
The two units serve different trades. Cubic centimetres, often written cc, dominate engineering: motorcycle and scooter engines are advertised by swept displacement — a '250cc' bike, a '650cc' twin — and medical syringes in many countries carry cc markings on the barrel. US fluid ounces instead measure consumer liquids: bottled beverages, cooking measurements, and vehicle fluid reservoirs on cars built or sold in the United States, where a coolant tank might be marked in fl oz even though the engine specification sheet quotes displacement in cc.
- Type your volume into the Cubic centimetres (cc) field; it opens at 500, half a litre, as a reference point.
- Read your result on the US fluid ounces (floz) line, recalculated to six decimal places on every keystroke.
- Entries accept thousandths, so precise figures like 12.5 or 237.5 cc convert without any loss of detail.
- Reversing direction? Multiply your fluid-ounce figure by 29.5735295625 to return to cubic centimetres exactly.
Worked example — a 500 cc coolant reservoir
An imported motorcycle's service manual specifies a coolant reservoir capacity of 500 cc, but the replacement coolant on an American parts-store shelf is labelled in fluid ounces instead. Type 500 into Cubic centimetres (cc) and US fluid ounces (floz) reads 16.9070113509 — enough to know that a standard 16.9 fl oz bottle, the same size as a common bottled-water container, falls just short of a full fill.
That same 16.9070113509 fl oz figure is worth remembering on its own: it is the exact conversion of a half-litre, since 500 cc and 500 ml describe the identical volume. Any spec sheet quoting 500 cc — an oil reservoir, a coolant tank, a syringe barrel — converts to this same fluid-ounce figure regardless of what liquid happens to be inside it.
Questions
Is one cc exactly 0.0338140227018 US fluid ounces?
As a rounded display, yes to thirteen decimal places — the true value is a repeating decimal that never terminates, because it is the reciprocal of 29.5735295625. Both underlying definitions are exact: a US gallon is precisely 231 cubic inches, an inch has been precisely 25.4 mm since 1959, and 128 fluid ounces make one gallon. Multiply those together and you get an exact millilitre figure per ounce; divide the other way and the endless decimal shown here is what results.
Is a cc the same thing as a millilitre?
Yes, exactly, since the 12th General Conference on Weights and Measures redefined the litre in 1964 as precisely one cubic decimetre. Before that, from 1901, a litre was instead defined as the volume of one kilogram of pure water at its densest point, a figure that turned out to be 1.000028 cubic decimetres — a tiny gap that briefly separated the two units before the 1964 decision closed it for good.
Why do engines and syringes use cc instead of ml?
Largely tradition. Engine displacement has been advertised in cubic centimetres since long before millilitre became the everyday household term, and manufacturers never saw a reason to switch a well-known marketing figure — a '400cc' motorcycle means exactly the same volume as a '400ml' one would. Medical settings, by contrast, increasingly favour ml specifically because a handwritten 'cc' can be misread as two zeros or as the abbreviation for units, a known source of dosing errors that ml sidesteps.
Is this the same as a UK or imperial fluid ounce?
No — mixing the two is a common and costly mistake. An imperial fluid ounce measures 28.4130625 ml, about 3.9% smaller than the US version, because Britain's imperial gallon — defined in 1824 and later fixed in law at exactly 4.54609 litres — divides into 160 ounces rather than 128. A 500 cc volume therefore reads 16.907 US fluid ounces but 17.598 imperial fluid ounces — a gap large enough to matter if you are filling something to a marked line.
Does 1 cc of a liquid always weigh close to 1 gram?
Only for substances near the density of water, and even then only approximately. Engine oil runs roughly 0.85 to 0.9 grams per cc, coolant concentrate closer to 1.1, and petrol around 0.75 — meaningfully lighter or heavier than plain water. Converting a volume in cc into a weight in ounces or grams requires the specific liquid's density, which this converter does not assume, since it converts volume to volume only.
What is the fastest way to sanity-check a cc-to-oz answer?
Remember that roughly 30 cc makes one fluid ounce — close enough for a rough estimate, since the exact figure is 29.5735295625. A quick division by 30 gets you within about 1.4% of the precise answer instantly, useful for spotting a typo or a misplaced decimal point before trusting a number pulled from a spec sheet or a converted recipe.