Convert ft³ to L cubic feet ↔ litres Free Online Secure
Type a value in cubic feet and read it in litres at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert ft³ to L (cubic feet ↔ litres)
| ft³ | L |
|---|---|
| 1 | 28.316846592 |
| 2 | 56.633693184 |
| 3 | 84.950539776 |
| 5 | 141.58423296 |
| 10 | 283.16846592 |
| 20 | 566.33693184 |
| 50 | 1415.8423296 |
| 100 | 2831.6846592 |
Where these units come from
The litre has an awkward history. From 1901 it was defined as the volume of one kilogram of pure water at its densest, which sounds elegant but came out at 1.000028 cubic decimetres — close enough to be confusing and far enough to spoil careful work. In 1964 the definition was abandoned and the litre became exactly one cubic decimetre, which it has been ever since. The gallon has a messier story still: the US gallon descends from the English wine gallon of 231 cubic inches, while Britain redefined its own in 1824 as the volume of ten pounds of water. Nobody reconciled the two, so a US gallon is 3.785411784 litres and an imperial gallon 4.54609 — about a fifth larger. The gallon, pint, cup, fluid ounce and spoons on this page are the US ones.
Where you meet them
Millilitres and litres run through daily life almost invisibly: bottles, fuel, paint, dosage, the capacity of a kettle. Cubic metres belong to water bills, concrete, shipping and the air a ventilation system has to move. Cubic centimetres name engine displacement, cubic feet appear in freight and in appliance capacities, and cups and spoons live almost entirely in recipes — which is exactly where the difference between a US cup and a metric one quietly ruins a cake.
Questions people ask
Where are cubic feet used?
In the United States for natural gas billing, refrigerator and freezer capacity, and the interior volume of shipping containers, and worldwide for airflow, where fans are rated in cubic feet per minute. A cubic foot is exactly 28.316846592 litres, so a small fridge of 4 cubic feet holds about 113 litres.
Is a litre of water really a kilogram?
Very nearly. The kilogram was first defined as the mass of one litre of water, and the two are still close: water at about 4 °C is 0.99997 kilograms per litre. It is not exact today because the kilogram is now defined from a physical constant. Warm water is slightly lighter, so the rule is a good approximation and not a law.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Scuba tanks, welding gas and propane: cubic feet of gas in litres
An American dive shop sells an aluminium tank rated at 80 cubic feet, a welding supplier sells argon in cylinders of 80 or 125 cubic feet, and a propane label gives the vapour in cubic feet per gallon. A European buyer thinks in litres. To convert ft³ to L you multiply by 28.3168: an 80 ft³ tank holds 2,265 L of gas at normal pressure, and a flow of 20 cubic feet per hour is 9.4 litres per minute. This page multiplies as you type, and the text below shows how the factor applies to divers, welders and anyone who cooks on propane.
The page covers the rule with examples, a note on each unit, a comparison, a tour of gas cylinders and the slips to avoid. All arithmetic happens in your browser; nothing you enter is sent anywhere.
How to convert ft³ to L: multiply by 28.3168
The rule
One cubic foot is exactly 28.316846592 litres, because a foot is 30.48 cm and 30.48 cubed is 28,316.85 cm³. To convert ft³ to L, multiply the cubic feet by 28.3168, or by 28.3 for a rough figure. So 1 ft³ is 28.3 L, 10 ft³ is 283.2 L and 80 ft³ is 2,265 L. In the other direction, divide litres by 28.3168.
Worked examples
A diver who breathes 0.5 ft³ per minute uses 14.2 litres per minute. A welding flow of 20 ft³ per hour is 566 litres per hour. A 20 lb propane cylinder gives about 171 ft³ of vapour, 4,843 litres. A party balloon of 0.4 ft³ holds 11.3 litres.
Why not 30.48
The figure 30.48 converts feet to centimetres. A volume in litres needs the cube divided by a thousand, which is 28.3. Using 30.48 leaves you about 8 percent too high, an error large enough to matter on a gas plan.
A quick sanity test
The litre is the smaller unit, so the number grows by nearly 28 times. If your “convert ft³ to L” calculation result grew by only three or by 30 times, a wrong factor was used.
The cubic foot
A cube one foot on each side
The cubic foot is 28.317 litres. In American industry it is the standard unit for gas volume, whether in a cylinder, a pipeline or a meter, usually referred to normal conditions of temperature and pressure.
Where it appears
Diving cylinders, welding gases, propane and natural gas, airflow and refrigeration.
The litre
A cube of ten centimetres
The litre is a thousand cubic centimetres. It is the unit of cylinder water capacity in most countries, and for gas flow at the regulator, litres per minute is the standard unit.
Where it appears
Cylinder markings, flow meters, European cylinders and medical gas.
Cubic foot and litre compared
A cubic foot holds about 28.3 litres. Gas figures can be misleading, since the volume of gas in a cylinder depends on pressure. A tank marked 80 cubic feet holds 2,265 litres at atmospheric pressure, but its internal water volume is only 11 litres. Both figures appear on the cylinder, in different units, and it is easy to mix them up.
The factor is not round, so estimates are approximate: multiply by 28 and add a little. For exact work, use 28.316846592.
Where the conversion appears
Diving cylinders
An aluminium 80 holds 80 ft³ of gas at 3,000 psi, which is 207 bar. Its internal volume is about 11.1 litres, so 11.1 times 207 gives roughly 2,300 litres. A steel 12 litre tank filled to 232 bar holds about 2,780 litres, or 98 ft³. A diver who knows both figures can compare American and European tanks.
Air consumption
A typical diver breathes 0.5 ft³ per minute at the surface, 14 litres. At 20 metres, where the pressure is three times as high, the same breath takes 1.5 ft³, 42.5 litres, from the tank. An 80 ft³ tank would last about 53 minutes at 20 metres, ignoring the reserve. Planning a dive starts with the “convert ft³ to L” calculation step.
Welding and propane
Argon flow for welding is set at 15 to 25 ft³ per hour, 7 to 12 litres per minute. A cylinder of 80 ft³ lasts four hours at 20 ft³ per hour. A gallon of liquid propane gives 36.4 ft³ of vapour, 1,030 litres. A 20 lb cylinder holds 4.7 gallons, so about 4,840 litres of vapour.
Rated capacity and internal volume
A tank's internal volume, in litres, is the water it would hold. Its gas capacity, in cubic feet, is how much gas it holds once compressed, expressed at normal pressure. The two are linked by pressure. A tank of 11.1 litres at 207 bar holds about 2,300 litres of gas, which is the 80 ft³ on the label. A smaller tank at a higher pressure can hold the same, and the two ways of describing it are equally correct.
In a spreadsheet
Put the cubic feet in column A and use =A2*28.316846592 in column B. For the reverse, =B2/28.316846592. A column for pressure and another for tank volume let you check the rated capacity: litres of water times bar gives litres of gas. Format the answers to the nearest litre, and keep the original column for audit.
Rounding
The factor is exact, so rounding is your choice. A cylinder labelled 80 ft³ gives 2,265 litres, but the real figure depends on the actual fill pressure and temperature, so quoting more than three significant figures is pointless. Round at the end of the calculation, and note the conditions to which the figure refers.
A mental shortcut
Multiply cubic feet by 28 and add 1 percent. For 10 ft³: 280 plus 2.8 is 282.8 litres, against 283.2 exactly. For 80 ft³: 2,240 plus 22.4 is 2,262, against 2,265. The error is a tenth of a percent, which is smaller than the variation in cylinder fill from one day to the next.
Reference values
1 ft³ is 28.3 L, 5 ft³ is 141.6 L, 10 ft³ is 283.2 L, 20 ft³ is 566 L, 40 ft³ is 1,133 L, 80 ft³ is 2,265 L, 100 ft³ is 2,832 L and 125 ft³ is 3,540 L. When you convert ft³ to L and land far from this ladder, repeat the multiplication.
Checking by reversing
To make sure your “convert ft³ to L” calculation result is right, divide it by 28.3168. If 80 ft³ gave 2,265 litres, then 2,265 divided by 28.3168 returns 80. Another check is the size of the number: it should be nearly 28 times larger. If it is 3 times larger or 30, a different factor was used.
Fire extinguishers
A 5 lb carbon dioxide extinguisher releases about 43.7 ft³ of gas, 1,237 litres, when discharged. In a small room of 100 ft³, 2,832 litres, that would raise the concentration of carbon dioxide to dangerous levels, which is why such extinguishers carry warnings. Safety officers convert the volume of gas to litres and compare it with the room volume in cubic metres, and a clear convert ft³ to L step avoids any misreading.
Mixed shielding gases
A popular welding mix of 75 percent argon and 25 percent carbon dioxide is sold in cylinders of 80 or 125 ft³. At a flow of 25 ft³ per hour, 11.8 litres per minute, an 80 ft³ cylinder lasts 3.2 hours. In a shop where several welders share a supply, the total flow in litres per minute is added and compared with the regulator limits, which are usually given in cubic feet per hour.
Nitrogen for tyres and purging
A car tyre of 30 litres inflated from atmospheric pressure to 2.2 bar absolute takes in about 36 litres of extra free gas, 1.3 ft³. Purging a pipeline with nitrogen is usually calculated in several volumes of the pipe, each in cubic feet or cubic metres. A 100 ft³ line purged six times needs 600 ft³, 17,000 litres. Because supply is bought by the cubic foot and the line is designed in metric, a conversion is part of the planning.
Forklift and camping cylinders
A forklift propane cylinder of 33 lb holds 7.8 gallons of liquid, which gives 284 ft³ of vapour, 8,040 litres. A camping cylinder of 1 lb holds 0.236 gallon and 8.6 ft³, 243 litres. The difference shows how fast a small stove can run through a cylinder. When you convert ft³ to L for each size, you can compare the cost per litre of gas, not per cylinder.
Soda fountains and beer systems
A keg of 15.5 gallons holds 58.7 litres, 2.07 ft³. A bar that pours forty kegs a month moves 83 ft³ of beer, 2,350 litres. The gas that pushes it, carbon dioxide or a nitrogen blend, is sold by the pound or the cubic foot, so a bar manager who wants the cost of gas per litre of beer must convert ft³ to L for the gas and divide by the litres poured.
Standard and actual cubic feet
The gas industry defines a standard cubic foot at a reference pressure and temperature, for example 14.7 psi and 70 °F. An actual cubic foot is whatever volume the gas has at the real conditions. A pipeline meter reports actual volumes and corrects them to standard. In litres, the same distinction holds: normal litres are at 0 °C and 1.013 bar, standard litres at 15 or 20 °C, and the conversion between the two is a few percent.
Ventilation of a workshop
A workshop of 30 by 20 by 10 feet has 6,000 ft³, 170 cubic metres. A fume extractor of 400 CFM, 11.3 cubic metres per minute, changes the air every 15 minutes. Regulations specify ventilation rates in litres per second per person or air changes per hour. A safety officer in one country reading a rule from another has to convert, and the factor of 28.3 is the first number to remember.
Cylinders for laboratories
A laboratory gas cylinder of size 300 holds about 300 ft³, 8,500 litres, at 2,200 psi. A smaller lecture bottle holds 1 to 10 ft³, 28 to 283 litres. Chemists order gas by the cylinder size, but flow meters on instruments read in litres or millilitres per minute. A run of 20 mL per minute uses 1.2 litres an hour, so a lecture bottle of 10 ft³ lasts about 236 hours, nearly ten days.
Inflatables and boats
An inflatable boat of 12 ft³, 340 litres, needs a pump stroke of 2 litres about 170 times at low pressure. A paddle board of 11 ft³ inflated to 15 psi absorbs about 22 ft³ of free air, 620 litres. Manuals describe volume in cubic feet and pressure in psi, so a European user who owns a litre pump has to convert ft³ to L to work out how many strokes to expect.
Propane and its vapour
A gallon of liquid propane expands to about 36.4 ft³ of vapour, which is 1,030 litres. A 20 lb cylinder holds 4.7 gallons, so 171 ft³, 4,843 litres. A barbecue burner uses about 0.1 to 0.3 ft³ of vapour per minute, depending on the setting, which is 3 to 8.5 litres per minute. A cylinder therefore lasts roughly 10 to 30 hours of burning.
Natural gas billing
Natural gas in the United States is billed by the hundred cubic feet, called a Ccf, or by the therm. A Ccf is 100 ft³, which is 2.83 m³ or 2,832 litres, and holds about 1.04 therms. Utilities convert volume to energy with a heating value factor. When you compare an American bill with a European one in cubic metres or kilowatt-hours, you convert ft³ to L first and then apply the factor.
Carbon dioxide cylinders
A 5 lb cylinder of carbon dioxide, used in beer systems and aquaria, holds about 43.7 ft³ of gas, 1,237 litres. At 9 psi pressure for a small aquarium diffuser, a few bubbles per second, the cylinder lasts for months. Brewers calculate how many kegs a cylinder can push, and the conversion from cubic feet to litres tells them how much gas each keg of 19 litres needs.
Helium and balloons
A latex balloon of 11 inches holds about 0.4 ft³, which is 11.4 litres, and lifts about 11 grams. A bundle of 50 balloons needs 20 ft³, 566 litres, of helium. A cylinder marked 125 ft³ holds 3,540 litres, enough for about 300 balloons. Party suppliers quote cylinders in cubic feet, so a European buyer wants the litres to estimate the number of balloons.
Oxygen and acetylene for cutting
A gas cutting set uses oxygen and acetylene. A large oxygen cylinder holds 250 ft³, 7,080 litres, and a smaller one 125 ft³, 3,540 litres. Acetylene cylinders are rated at 60 or 100 ft³, 1,700 or 2,830 litres. The ratio of oxygen to fuel is about 1 to 1 for a neutral flame, so you need as much of one as of the other for a long cut. The conversion lets you compare sets from different regions.
Compressed air tanks
A portable air tank of 10 gallons, 1.34 ft³, 37.9 litres, filled to 125 psi, holds the equivalent of about 12.7 ft³ of free air, 360 litres. A tool that draws 4 CFM, 113 litres per minute, would empty that in a little over three minutes. Compressor makers quote the delivered flow in CFM at a stated pressure, the tank size in gallons, and the user wants litres.
Cave and dive logs
Logbooks record consumption as a surface air consumption rate, in cubic feet per minute or litres per minute. A diver using 0.6 ft³ per minute has a rate of 17 litres. After a 45 minute dive at 10 metres, where the pressure is twice the surface, the diver has used 54 ft³, 1,530 litres. Instructors teach both systems, and a quick conversion helps students from different countries compare their numbers.
More values for convert ft³ to L
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 ft³ = 2.8316846592 L
- 0.5 ft³ = 14.158423296 L
- 3 ft³ = 84.950539776 L
- 4 ft³ = 113.267386368 L
- 7 ft³ = 198.217926144 L
- 15 ft³ = 424.75269888 L
- 20 ft³ = 566.33693184 L
- 75 ft³ = 2,123.7634944 L
- 200 ft³ = 5,663.3693184 L
- 500 ft³ = 14,158.423296 L
- 2,000 ft³ = 56,633.693184 L
- 10,000 ft³ = 283,168.46592 L
Mistakes when you convert ft³ to L
Using 30.48
That is the factor for lengths. For volume in litres, multiply by 28.3168.
Mixing gas capacity and tank volume
80 ft³ is gas capacity at normal pressure; 11 litres is the water volume. They describe the same tank in different ways.
Ignoring conditions
Gas volume depends on pressure and temperature. Check whether a figure is standard or actual before comparing.
Quick answers
How many litres are in a cubic foot?
28.3168.
How do I convert ft³ to L?
Multiply by 28.3168.
How many cubic feet are in a litre?
0.0353147.
What is 80 ft³ in litres?
2,265 L.
Is my number kept anywhere?
No, it stays in your browser.
More pages and a closing note
For other volume conversions, see Convert ft³ to yd³, Convert ft³ to m³, Convert gal to L, Convert fl oz to L, Convert L to fl oz, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The opposite direction is Convert L to ft³.
In short, you convert ft³ to L by multiplying by 28.3168, the cube of 30.48 divided by a thousand, and writing the unit beside the answer. Your figure is calculated on your own device, with no account and no upload.