To find circumference – multiply the diameter by 3.1416; or, divide diameter by 0.3183.
To find diameter – multiply the circumference by 0.3183; or, divide circumference by 3.1416.
To find radius – multiply the circumference by 0.15915; or, divide circumference by 6.28318;
or, divide diameter by 2.
To find the side of a square to be inscribed in a circle – multiply diameter by 0.7071; or,
multiply the circumference by 0.2251; or, divide the circumference by 4.4428.
To find the side of a square to equal the area of a circle – multiply the diameter by 0.8862;
or, divide diameter by 1,1284; or, multiply the circumference by 0.2821; or, divide circumference
To find the area of a circle – multiply the circumference by one-quarter of the diameter; or,
multiply the square of the diameter by 0.7854; or, multiply the square of the circumference by
0.7958; or, multiply the square of one-half the diameter by 3.1416.
Doubling the diameter of a circle increases the area 4 times.
A side multiplied by 1.412 = the diameter of a circle which will circumscribe the given square.
A side multiplied by 4.443 = the circumference of its circumscribing circle.
A side multiplied by 1.1284 = the diameter of a circle equal in area to that given square.
A side multiplied by 3.545 = circumference of an equal circle.
To find diagonal of a square – multiply side by 1.4142.
To find the area of an ellipse – multiply the product of its axes by 0.7854; or, multiply the product of its semi-axes by 3.14159.
Contents of a cylinder = area of end X length.
Contents of a wedge = area of triangular base X altitude.
Surface of a cylinder = length X circumference plus area of both ends.
Surface of a sphere = diameter squared X 3.1416; or, diameter X circumference.
Contents of a sphere = diameter cubed X 0.5236.
Contents of a pyramid or cone, right or oblique, regular or irregular = area of base X one-third of the altitude.
Area of a triangle = base X one-half the altitude.
Area of parallelogram = base X altitude.
Area of trapezoid = altitude X one-half the sum of parallel sides.
To find distance across the corners of hexagons – multiply the distance across the flats by 1.1547.
1 gal. water = 8.3 lb.
1 hp = 745.2 watts.
1 BTU = .252 kg calories = 0.2930 watt hours.
1 BTU per lb. = 1.8 cal per gram.
1 kw-hr = 3412 BTU per hour.
1 kw-hr will evaporate 3.5 lb of water at 212°F.
1 kw-hr will raise 22.75 lb of water from 62°F to 212°F.
1 gal. = 231 cu.in. = 3.785 liters = .1337 cu.ft.
1 cu.ft. = 1728 cu.in. = .03704 cu.yd. = 7.481 gal.
To find the equivalent, in terms of a unit in the customary system, of a given number of metric units, multiply or divide their number (as indicated) by the factor shown.
Thus: 10 millimeters are equivalent to 10 x 0.03937 inches or to 10 ÷ 25.4 inches.
Millimeters x .03937 = inches; or ÷ 25.4 = inches.
Centimeters x .03937 = inches; or ÷ 25.4 = inches.
Meters x 39.37 = inches.
Meters x 3.28 = feet.
Kilometers x 3280.8 = feet.
Square meters x 10.764 = square feet.
Cubic centimeters ÷ 16.387 = cubic inches.
Cubic centimeters ÷ 3.70 = fluid drams (U.S.P.).
Cubic centimeters ÷ 29.57 = fluid ounces (U.S.P.).
Cubic centimeters ÷ 3.531 x 10 -5 = cubic feet.
Cubic meters x 35.314 = cubic feet.
Liters x 61.025 = cubic inches.
Liters x 33.81 = fluid ounces (U.S.P.).
Liters x .2642 = gallons (231 cubic inches).
Liters ÷ 3.785 = gallons (231 cubic inches).
Liters ÷ 28.317 = cubic feet.
Grams x 15.432 = grains.
Grams (water) ÷ 29.57 = fluid ounces.
Grams ÷ 28.35 = ounces avoirdupois.
Grams per cubic centimeter ÷ 27.7 = pounds per cubic inch.
Kilograms x 2.2046 = pounds.
Kilograms x 35.3 = ounces avoirdupois.
Kilograms per square centimeter x 14.223 = pounds per square inch.
Kilo per meter x .672 = pounds per foot.
Kilo per cubic meter x .062 = pounds per cubic foot.
Kilowatts x 1.34 = h.p. (33,000 foot pounds per minute).
Watts ÷ 746 = horse power.
Centigrade x 1.8 + 32 = degrees Fahrenheit.