How this instrument works
Volume scales as length cubed, which is all a cubic foot ever was: one foot, taken three times over. Since 1959, when standards bodies across six countries settled on one common definition, an international foot has measured exactly 0.3048 m — so 0.028316846592 m3 comes out of arithmetic rather than measurement. Watch it terminate: 3048 × 3048 × 3048 = 28,316,846,592, and dividing by one trillion merely shifts decimal points. Twelve places, then zeros forever.
Same volume reads as 28.316846592 litres, litres having been exactly one cubic decimetre apiece since 1964, when metrologists abandoned older wording tied to kilograms of water. Useful anchors follow from there: 1 m3 is 1000 litres; one cubic yard is 27 ft3, or 0.764554857984 m3; a 20-foot shipping container encloses about 1170 cubic feet, near enough 33 m3 of cargo space.
Both units remain in hard commercial use, rarely side by side. American gas and water utilities meter in CCF — one hundred cubic feet — and count reserves in trillions; showrooms sell refrigerators by cubic-foot capacity; ventilation engineers size fans in CFM, where each unit works out at 1.69901079552 m3 per hour. Elsewhere gas arrives in m3, ready-mixed concrete is ordered in m3, and freight is priced on its cube. Any trade crossing that boundary multiplies by 0.028316846592 all day long.
- Type a volume into the Cubic feet (ft3) field. It opens at 100, which is one CCF on an American gas or water meter.
- Read your answer on the Cubic metres (m3) line — it lands on every keystroke, carried to six decimal places.
- Working from a drawing in feet? Multiply length by width by depth first, then enter that single ft3 figure.
- Need traffic in reverse? Divide your cubic metres by 0.028316846592, or multiply by 35.3146667215 — that reciprocal, rounded off.
Worked example — 100 cubic feet, twice over
Ship tonnage began as volume, not weight: one gross register ton meant 100 cubic feet of permanently enclosed space, so a 500-ton schooner carried 50,000 of them below deck. Enter 100 in the Cubic feet (ft3) field and Cubic metres (m3) returns 2.8316846592, displayed as 2.831685 at six decimals — one register ton wearing metric dress, which is roughly what those 1969 tonnage rules replaced with dimensionless numbers.
Same 100 turns up on American utility bills as 1 CCF, one hundred cubic feet of gas passing your meter. Check it by hand: 0.028316846592 multiplied by 100 shifts its decimal point two places right, giving 2.8316846592 with nothing lost — 2831.68 litres of methane, priced abroad in m3. No quantity here was ever measured; every digit descends from definitions, and rounding waits until display.
Questions
Is 0.028316846592 exact, or has it been rounded?
Exact. It is 0.3048 cubed, and 0.3048 m is a legal definition of an international foot, agreed in 1959 between standards bodies in the United States, United Kingdom, Canada, Australia, New Zealand and South Africa. Cubing a four-decimal terminating number yields a twelve-decimal terminating number, so an entire factor fits on screen with no tail left hiding. Rounding creeps in only where results reach six displayed decimals.
Why can I not just multiply my volume by 0.3048?
Because 0.3048 shrinks one dimension, and volume has three. Length, width and depth each scale by 0.3048, so volume scales by 0.3048 cubed. Using 0.3048 alone overstates an answer by a factor of 10.7639104 — which is not a random error, it is precisely how many square feet sit in a square metre. Reversing direction sets an identical trap: 1 m3 is 35.31 cubic feet, never 3.28.
Do imperial and US customary cubic feet differ?
No. Both systems took on that same 0.3048 m foot in 1959, so cubic feet mean one identical quantity worldwide — unlike gallons, bushels and barrels, where imperial and American measures parted company centuries ago and never reconciled. Ask whose gallon before converting; never ask whose foot. Oil trading shows this working: 42 US gallons make one barrel, that barrel occupies 5.614583 cubic feet, and it lands on 0.158987 m3 whichever exchange quotes it.
What about volumes measured with a US survey foot?
NIST and NOAA retired that foot at close of 2022. A survey foot measured 1200/3937 m, roughly two parts per million longer than an international foot, and cubing triples any such gap: one cubic survey foot comes to 0.0283170165 m3, six parts per million larger. Around basements or truckloads that difference vanishes; spread across a million acre-feet of stored water it reaches some 7400 m3, so hydrology archives are worth checking for which foot was in force.
Does 100 standard cubic feet of gas equal 2.83 normal cubic metres?
Not directly, because gas volumes carry reference conditions and those two do not match. A standard cubic foot in US practice is referenced to 60 degrees Fahrenheit and 14.696 psia, while a normal cubic metre assumes 0 degrees Celsius at 101.325 kPa. Geometry gives 2.8316846592 m3, then a temperature correction of about 0.9461 brings you near 2.679 Nm3 of equivalent gas. Confusing those two is a classic energy-trading error.
How many cubic feet fit inside one cubic metre?
35.31466672148859… — reciprocal of that exact factor. Its decimals never stop, yet nothing about them is uncertain, since 35.3146667… is simply an ordinary fraction, 1953125000/55306341, whose digits eventually repeat. Rounding to 35.3147 for mental arithmetic costs about one part per million, far finer than any tape measure, meter or concrete truck will ever notice.