Convert ft³ to m³ cubic feet ↔ cubic metres Free Online Secure
Type a value in cubic feet and read it in cubic metres at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
Nothing uploaded
Common values — Convert ft³ to m³ (cubic feet ↔ cubic metres)
| ft³ | m³ |
|---|---|
| 1 | 0.028316846592 |
| 2 | 0.056633693184 |
| 3 | 0.084950539776 |
| 5 | 0.14158423296 |
| 10 | 0.28316846592 |
| 20 | 0.56633693184 |
| 50 | 1.4158423296 |
| 100 | 2.8316846592 |
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.
How many litres are in a cubic metre?
1000, since a cubic metre is a cube of ten decimetres on each side, and a litre is one cubic decimetre. A cubic metre of water weighs about a tonne. Water and gas consumption are billed in cubic metres, and a bath of 150 litres is therefore 0.15 of one.
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.
Rivers, reservoirs and acre-feet: water volumes in cubic metres
American water engineers measure the flow of a river in cubic feet per second, the storage in a reservoir in acre-feet and the volume of a flood in cubic feet. To compare any of it with a European report in cubic metres, you need one factor: to convert ft³ to m³ you multiply by 0.0283168. A river running at 10,000 cubic feet per second therefore carries 283 cubic metres each second, and an acre-foot of 43,560 cubic feet is 1,233 cubic metres. This page multiplies as you type, and the text below walks through rivers, dams and irrigation.
The page covers the rule with examples, a short note on each unit, a comparison, a tour of hydrology and the slips to avoid. All arithmetic happens in your browser; nothing you enter is sent anywhere.
How to convert ft³ to m³: multiply by 0.0283168
The rule
One cubic foot is exactly 0.028316846592 cubic metres, because a foot is 0.3048 m and 0.3048 cubed is 0.0283168. To convert ft³ to m³, multiply the cubic feet by 0.0283168, or divide by 35.3 for a rough figure. So 100 ft³ is 2.83 m³, 1,000 ft³ is 28.3 m³ and 43,560 ft³ is 1,233.5 m³. In the other direction, multiply cubic metres by 35.3147.
Worked examples
A flow of 85,000 cubic feet per second, the average of Niagara Falls, is 2,407 cubic metres per second. A flood of 8.64 billion cubic feet is 245 million cubic metres. One inch of rain on an acre, 3,630 ft³, is 102.8 m³. For a quick estimate divide by 35: 700 ft³ is about 20 m³.
Why not 0.3048
The number 0.3048 converts feet to metres. A volume multiplies three lengths, so the factor is 0.3048 cubed. Using 0.3048 on a volume leaves the answer nearly eleven times too large, which for a reservoir is a rather expensive mistake.
A quick sanity check
The cubic metre is the larger unit, so the figure shrinks by about a factor of 35. If your “convert ft³ to m³” calculation result shrank by only three times, you used the length factor.
The cubic foot
A foot in every direction
The cubic foot is 0.0283 cubic metres, 28.3 litres. In American hydrology it appears as a volume in flood studies and, per second, as the flow rate known as the cusec.
Where it appears
River gauges, flood reports, water rights, pumping specifications and drainage design.
The cubic metre
A metre in every direction
The cubic metre is the SI unit of volume, a thousand litres. Water supply, reservoirs and flow rates around the world use it, and cubic metres per second is the standard unit for river discharge.
Where it appears
International hydrology, water utilities, dams and drainage, and environmental reports.
Cubic foot and cubic metre compared
A cubic metre holds about 35.3 cubic feet. A flow quoted as 10,000 cfs sounds enormous, and in cubic metres per second it is still 283, since the factor of 35 simply shrinks the figure. People comparing floods between countries should be sure they are comparing like with like, and not a flow in cfs with a volume in cubic metres.
The factor is not round, so mental conversions are approximate: divide by 35, or multiply by 0.028. For reports, use the exact 0.028316846592.
Where the conversion appears
River flows
The Mississippi averages around 593,000 cfs at its mouth, which is 16,800 m³/s. Niagara is about 85,000 cfs, 2,400 m³/s. A small stream of 50 cfs carries 1.4 m³/s. Gauge data in the United States comes in cfs, while European data is in cubic metres per second, so comparisons start with the factor 0.0283.
Acre-feet and reservoirs
An acre-foot is the volume of water covering an acre to a depth of a foot: 43,560 ft³, 1,233.5 m³. Lake Mead holds roughly 28 million acre-feet at full pool, about 35 cubic kilometres. A household might use about 0.4 acre-feet a year, around 500 m³. When you convert ft³ to m³ for these figures, they become comparable with European reservoirs.
Floods and storage
A flow of 50,000 cfs for two days brings 8.64 billion cubic feet, 245 million m³ of water. A flood storage basin that holds 10 million ft³, 283,000 m³, could not contain it. Engineers compare inflow volume with capacity, so the two must be in the same unit.
Acre-inches and rainfall
One inch of rain falling on one acre is an acre-inch, which is 3,630 ft³ or 102.8 m³, about 27,154 US gallons. A storm of 3 inches over a catchment of 1,000 acres delivers 3,000 acre-inches, 10.9 million ft³, 308,000 m³. Hydrologists use acre-inches and cubic feet interchangeably in the United States, and a conversion links the numbers to European millimetres of rain over hectares.
Swimming pools and tanks
An Olympic pool holds about 88,000 ft³, which is 2,500 m³. A backyard pool of 800 ft³ has 22.7 m³. A municipal storage tank of 1 million gallons is 133,700 ft³, 3,785 m³. Because each measure appears in manuals for filters, chemicals and pumps, an operator has to convert ft³ to m³ and keep the results in a log.
Wetlands and ponds
A pond of 2 acres and an average depth of 4 feet has 8 acre-feet, 348,480 ft³, 9,868 m³. Evaporation of 3 feet a year from the surface removes 6 acre-feet, 7,400 m³. Pond managers compare inflow and loss, usually in acre-feet or cubic feet per second, and a conversion lets them check against European studies in cubic metres.
Groundwater and wells
A well that pumps 20 gallons a minute produces 0.0446 cfs, 0.00126 m³/s, and over a year some 10.5 million gallons, 1.4 million ft³, 40,000 m³. Aquifers are described in acre-feet of storage. A basin with 5 million acre-feet holds 6.2 km³, and any withdrawals are compared with that figure in whichever units the report uses.
In a spreadsheet
Put the cubic feet in column A and use =A2*0.028316846592 in column B. For the reverse, =B2/0.028316846592. A column with =A2*43560 converts acre-feet to cubic feet, and =A2*1233.48 acre-feet to cubic metres. Format with no decimals for large volumes, and keep the source column so the calculation can be audited.
Rounding
The factor is exact, so rounding is your decision. Hydrological data is rarely better than three significant figures, so a flow of 10,000 cfs gives 283 m³/s, not 283.168. Round at the end of the calculation. In a flood study, state the rounding rule so that readers can retrace your numbers.
A mental shortcut
Divide cubic feet by 35. For 1,400 ft³ the answer is 40 m³, against 39.6 exactly. For 7,000, 200 against 198. The error is under 1 percent. For flows in cfs, divide by 35 as well: 3,500 cfs is about 100 m³/s. The trick is accurate enough for a first look at gauge data.
Reference values
1 ft³ is 0.0283 m³, 35.3 ft³ is 1 m³, 100 ft³ is 2.83 m³, 1,000 ft³ is 28.3 m³, 10,000 ft³ is 283 m³, 43,560 ft³ is 1,233 m³ and 1,000,000 ft³ is 28,317 m³. If you convert ft³ to m³ and land far from this ladder, repeat the multiplication.
Checking by reversing
To make sure your “convert ft³ to m³” calculation result is right, multiply it by 35.3147. If 1,000 ft³ gave 28.3 m³, then 28.3 times 35.3147 returns about 1,000. A second check is the size of the result: it should be about 35 times smaller. If it is only 3 times smaller, you used 0.3048.
Navigation locks
A large river lock of 600 by 110 feet with a lift of 50 feet uses 3.3 million ft³ of water at each passage, about 93,400 m³. Twenty passages a day empty 1.9 million m³ downstream. Lock operators measure in cubic feet and feet of lift, while European waterway authorities report cubic metres per lockage, and a quick convert ft³ to m³ step puts the two on a par.
Fish hatcheries and raceways
A hatchery raceway of 100 by 10 feet with 3 feet of water holds 3,000 ft³, 85 m³. A flow of 5 cfs, 0.14 m³/s, changes the water roughly every 10 minutes. Fish densities are stated in pounds per cubic foot or kilograms per cubic metre, so a farmer comparing guidelines from the United States and Europe converts both the volume and the weight.
A cusec for a day
A flow of one cubic foot per second, kept up for 24 hours, delivers 86,400 ft³, which is 1.98 acre-feet or 2,447 m³. This convenient rule says that 1 cfs-day is almost exactly 2 acre-feet. A stream that flows at 5 cfs for a month therefore supplies about 300 acre-feet, 370,000 m³. Water managers use such rules to translate flow into storage.
Fire flow and hydrants
A fire department may need 1,500 gallons per minute for an hour, which is 90,000 gallons, 12,000 ft³ or 340 m³. A hydrant that gives 1,000 gpm supplies 2.23 cfs, 0.063 m³/s. Planners of water mains check that tanks and pipes can deliver such volumes, and reports in cubic feet or gallons need conversion to compare with European standards in litres per second.
Water towers and tanks
A water tower of 500,000 gallons holds 66,800 ft³, which is 1,893 m³. At a city use of 100 gallons per person per day, it serves 5,000 people for a day. A ground tank of 5 million gallons has 668,000 ft³, 18,900 m³. Tank sizes are given in gallons in the United States, and comparisons with European figures in cubic metres need a clean conversion through cubic feet.
Sediment and dredging
A dredging contract may call for the removal of 250,000 cubic yards of sediment from a harbour, which is 6.75 million ft³ or 191,000 m³. A hopper dredger carrying 3,000 m³ per trip would make 64 trips. Project documents from American agencies state volumes in cubic yards or cubic feet, while the dredger specifications are in cubic metres, and the person who budgets the trips has to convert between them with care.
Mine water and pit lakes
A flooded quarry of 400 by 300 feet with an average depth of 40 feet holds 4.8 million ft³ of water, 136,000 m³. Pumping it out at 2,000 gallons per minute, 0.126 m³/s, would take about 12.5 days. Mine engineers quote rates in gallons per minute and volumes in cubic feet or acre-feet, and any report to a regulator abroad needs the totals in cubic metres.
Dams and what they hold
Hoover Dam is made of about 3.25 million cubic yards of concrete, which is 87.8 million ft³ or 2.48 million m³. The reservoir behind it holds some 35 km³ of water when full, about 14 times the volume of the dam itself, which is a fraction of what it holds. Comparing the numbers is easy once you convert ft³ to m³ for the dam and the lake, which shows how a conversion helps with scale.
City water supply
An American city that uses 100 million gallons a day, 100 MGD, draws 13.4 million ft³, which is 379,000 m³. A European city of the same size would report 380,000 m³ per day. Utilities in the United States speak of gallons or cubic feet, while those in Europe use cubic metres, so a factor appears in every comparison of per-capita use.
Pump ratings
A pump rated at 1,000 gallons per minute moves 2.23 ft³ per second, 0.063 m³ per second, 227 m³ per hour. A larger pump of 10,000 gpm would move 22.3 cfs, 0.63 m³/s. Pump curves give flow in gpm and head in feet, so a designer working to metric standards converts both. The cubic-foot step comes in when comparing with irrigation demands given in cfs.
Irrigation depth and volume
To put one foot of water on an acre needs 43,560 ft³, 1,233.5 m³. To irrigate 100 acres to a depth of 6 inches takes 50 acre-feet, 2.18 million ft³, 61,700 m³. The same job on 40 hectares to a depth of 15 cm is 60,000 m³, close enough to show that the two systems tell the same story with different numbers. A “convert ft³ to m³” calculation gives the link.
Culverts and storm drains
A pipe of 36 inches diameter running full at 3 feet per second carries 21 ft³ per second, 0.6 m³ per second. A storm drain of 5 feet diameter at the same speed carries 59 cfs, 1.67 m³/s. Drainage standards give capacity in cfs, while European standards use litres per second or m³/s, so the conversion matters for engineers who design drains to both.
Snowmelt and water supply
Water managers in dry regions forecast how much water the snowpack will deliver in spring. A basin whose snow holds 400,000 acre-feet, 493 million m³ of water, will yield an average flow of 2,000 cfs, 57 m³/s, over about 100 days. The forecast is stated in acre-feet, while flows are in cfs, and users from outside the United States convert both into cubic metres.
Hydropower
The power from falling water is density times gravity times flow times head. A flow of 1,000 cfs, 28.3 m³/s, falling 100 feet, 30.5 m, gives about 8.5 megawatts at ideal efficiency, and about 7.4 at 87 percent. Hydropower engineers use feet and cfs, so the cubic-foot conversion is a standard step when sharing design numbers with colleagues abroad.
More values for convert ft³ to m³
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 = 0.00283168 m³
- 0.5 ft³ = 0.014158423296 m³
- 3 ft³ = 0.084950539776 m³
- 4 ft³ = 0.113267386368 m³
- 7 ft³ = 0.198217926144 m³
- 15 ft³ = 0.42475269888 m³
- 20 ft³ = 0.56633693184 m³
- 75 ft³ = 2.1237634944 m³
- 200 ft³ = 5.6633693184 m³
- 500 ft³ = 14.158423296 m³
- 2,000 ft³ = 56.633693184 m³
- 10,000 ft³ = 283.16846592 m³
Mistakes when you convert ft³ to m³
Using 0.3048
That is the factor for lengths. For volumes, multiply by 0.0283168.
Mixing flow and volume
Cubic feet per second is a flow, cubic feet is a volume. Check the time unit before you compare numbers.
Forgetting the acre-foot
An acre-foot is 43,560 cubic feet, not 1,000 or 1,233. The figure 1,233 is its value in cubic metres.
Quick answers
How many cubic metres are in a cubic foot?
0.0283168.
How do I convert ft³ to m³?
Multiply by 0.0283168.
How many cubic feet are in a cubic metre?
35.3147.
What is 1,000 ft³ in cubic metres?
28.3 m³.
Is the number I type stored anywhere?
No, it stays in your browser.
More pages and a closing note
For other volume conversions, see Convert ft³ to L, Convert ft³ to in³, Convert yd³ to m³, Convert cm³ to m³, Convert m³ to yd³, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The opposite direction is Convert m³ to ft³.
In short, you convert ft³ to m³ by multiplying by 0.0283168, the cube of 0.3048, and writing the unit beside the answer. Your figure is calculated on your own device, with no account and no upload.