Depends On How You Measure It.

Common Formulas

AREA
Triangle:	A = (ab)/2 , in which a is the base and b the height.
Square:	A = a2, in which a is one of the sides.
Rectangle:	A = ab, in which a is the base and b the height.
Trapezoid:	A = (h(a + b))/2, in which h is the height, a the longer parallel side, and b the shorter.
Regular Pentagon:	A = 1.720a2, in which a is one of the sides.
Regular Hexagon:	A = 2.598a2, in which a is one of the sides.
Regular Octagon:	A = 4.828a2, in which a is one of the sides.
Circle:	A = πr2, in which π is 3.1416 and r the radius.
VOLUME
Cube:	V = a3, in which a is one of the edges.
Rectangular Prism:	V = abc, in which a is the length, b is the width, and c the depth.
Pyramid:	V = (Ah)/3, in which A is the area of the base and h the height.
Cylinder:	V = πr2h, in which π is 3.1416, r the radius of the base, and h the height.
Cone:	V = (πr2h)/3, in which π is 3.1416, r theradius of the base, and h the height.
Sphere:	V = (4πr3)/3, in which π is 3.1416 and r the radius.
TEMPERATURE SCALES
Degrees Fahrenheit to Degrees Celsius:	TC = 5/9 (TF – 32)
Degrees Celsius to Degrees Fahrenheit:	TF = 9/5 TC + 32
Degrees Celsius to Kelvins:	TK = TC + 273.15
CIRCUMFERENCE
Circle:	C = πd, in which π is 3.1416 and d the diameter.

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