The 'volume' of a solid object is the three-
dimensional concept of how much space it occupies, often quantified numerically. One-dimensional figures (such as
lines) and two-dimensional shapes (such as
squares) are assigned zero volume in the three-dimensional space.
Volumes of straight-edged and circular shapes are calculated using arithmetic formulas. Volumes of other curved shapes are calculated using
integral calculus, by approximating the given body with a large amount of small
cubes or concentric
cylindrical shells, and adding the individual volumes of those shapes. The volume of irregularly shaped objects can be determined by
displacement. If an irregularly shaped object floats on water, you will need a heavier object like a rock or metal and attach it on you floating object. This should cause the object to sink. Then, get the volume of the object. Subtract the volume of the attached heavy object and the original findings.
The generalization of volume to arbitrarily many dimensions is called
content. In
differential geometry, volume is expressed by means of the
volume form.
Volume and Capacity are sometimes distinguished, with capacity being used for how much a container can hold (with contents measured commonly in
litres or its derived units), and volume being how much space an object displaces (commonly measured in
cubic metres or its derived units).
Volume and capacity are also distinguished in a capacity management setting, where capacity is defined as volume over a specified time period.
Volume is a fundamental parameter in
thermodynamics and it is
conjugate to
pressure.
Volume formulae
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|-
! colspan = 3 | Common
equations for volume:
|-
!Shape
!Equation
!Variables
|-
|A
cube:
|
|''s'' = length of a side
|-
|A rectangular
prism:
|
|l = ''l''ength, w = ''w''idth, h = ''h''eight
|-
|A
cylinder (circular prism):
|
|''r'' = radius of circular face, ''h'' = height
|-
|Any prism that has a constant cross sectional area along the height
★
★ :
|
|''A'' = area of the base, ''h'' = height
|-
|A
sphere:
|
|''r'' = radius of sphere
which is the
integral of the
Surface Area of a
sphere
|-
|An
ellipsoid:
|
|''a'', ''b'', ''c'' = semi-axes of ellipsoid
|-
|A
pyramid:
|
|l = ''l''ength, w = ''w''idth, h = ''h''eight
|-
|A
cone (circular-based pyramid):
|
|''r'' = radius of
circle at base, ''h'' = distance from base to tip
|-
|Any figure (
calculus required)
|
|''h'' = any dimension of the figure, ''A''(''h'') = area of the cross-sections perpendicular to ''h'' described as a function of the position along ''h''
this will work for any figure if its cross-sectional area can be determined from h (no matter if the prism is slanted or the cross-sections change shape).
|}
(The units of volume depend on the units of length - if the lengths are in metres, th'''Bold text''Bold text''e volume will be in cubic 'metres', etc)
The volume of a
parallelepiped is the absolute value of the
scalar triple product of the subtending vectors, or equivalently the absolute value of the
determinant of the corresponding matrix.
The volume of any
tetrahedron, given its vertices 'a', 'b', 'c' and 'd', is (1/6)·|
det('a'−'b', 'b'−'c', 'c'−'d')|, or any other combination of pairs of vertices that form a simply connected
graph.
Volume measures: USA
U.S. customary units of volume:
★ U.S. fluid
ounce, about 29.6 mL
★ U.S. liquid
pint = 16 fluid ounces, or about 473 mL
★ U.S. dry pint = 1/64 U.S.
bushel, or about 551 mL (used for things such as blueberries)
★ U.S. liquid
quart = 32 fluid ounces, or about 946 mL
★ U.S. dry quart = 1/32 U.S. bushel, or about 1.101 L
★ U.S. liquid
gallon = 128 fluid ounces or four U.S. quarts, about 3.785 L
★ U.S. dry gallon = 1/8 U.S. bushel, or about 4.405 L
★ U.S. (dry level) bushel = 2150.42 cubic inches, or about 35.239 L
The 'acre foot' is often used in measuring the volume of water in a
reservoir or an
aquifer. It is the volume of water that would cover an
area of one
acre to a depth of one
foot. It is equivalent to 43,560 cubic feet or exactly 1233.481 837 547 52 m³.
★
cubic inch = 16.387064 cm
3
★
cubic foot = 1,728 in
3 ≈ 28.317 dm
3
★
cubic yard = 27 ft
3 ≈ 0.7646 m
3
★
cubic mile = 5,451,776,000 yd
3 = 3,379,200 acre-feet ≈ 4.168 km
3
Volume measures: UK
The UK is undergoing
metrication and is increasingly using the
SI metric system's units of volume, i.e.
cubic meter and
litre. However, some former units of volume are still in varying degrees of usage:
Imperial units of volume:
★ UK fluid
ounce, about 28.4 mL (this equals the volume of an avoirdupois ounce of water under certain conditions)
★ UK
pint = 20 fluid ounces, or about 568 mL
★ UK
quart = 40 ounces or two pints1.137 L
★ UK
gallon = 4 quarts, or exactly 4.546 09 L
The quart is now obsolete and the fluid ounce extremely rare. The gallon is only used for transportation uses, (it is illegal for petrol and diesel to be sold by the gallon). The pint is the only Imperial unit that is in everyday use, for the sale of draught beer and cider (bottled and canned beer is mainly sold in SI units) and for milk (this too is increasingly being sold in SI units, mainly Liters).
Volume measures: cooking
Traditional cooking measures for volume also include:
★
teaspoon = 1/6 U.S. fluid ounce (about 4.929 mL)
★ teaspoon = 1/6 Imperial fluid ounce (about 4.736 mL)
★ teaspoon = 5 mL (metric)
★
tablespoon = ½ U.S. fluid ounce or 3 teaspoons (about 14.79 mL)
★ tablespoon = ½ Imperial fluid ounce or 3 teaspoons (about 14.21 mL)
★ tablespoon = 15 mL or 3 teaspoons (metric)
★ tablespoon = 5
fluidrams (about 17.76 mL) (British)
★
cup = 8 U.S. fluid ounces or ½ U.S. liquid pint (about 237 mL)
★ cup = 8 Imperial fluid ounces or ½ fluid pint (about 227 mL)
★ cup = 250 mL (metric)
Relationship to density
The volume of an object is
equal to its
mass divided by its
average density. This is a rearrangement of the calculation of density as mass per unit volume.
The term ''
specific volume'' is used for volume divided by mass. This is the
reciprocal of the
mass density, expressed in units such as cubic meters per kilogram (m³·kg
-1).
See also
★
Area
★
Conversion of units
★
Density
★
Orders of magnitude (volume)
★
Mass
★
Ton (volume)
External links
★
FORTRAN code for finding volumes of various shapes