Here are just a few helpful nautical and metric equivalents. There are sometimes inconsistencies between sources on many of the measurements and values, so I’ll be quick to disclaim any responsibility if you use them and get yourself into a jam.

If you’d like to add any as a useful resource and reference for yourself or others, drop me an email.

Mike O. sent me this really good email, which I want to share with you:

“Commander Bob, one thing that is important about conversion factors is developing intuition… such as, for any temperature you want to experience, convert C to F by simply doubling it and add 30. That’s within 1 or 2 degrees F. which is close enough for most applications.”

“Likewise, liters and quarts are interchangeble to any precision outside a lab or not involving 100’s of gallons.”

(Thanks for your contribution, Mike. Shortcuts help make it an easier job.)

Isolines are lines on maps or charts to represent points of equal value. Here is a list of most of the isoline terms. You’ll see some on nautical charts, and others are more obscure. Don’t try and commit all of them to memory, but perhaps knowing which ones pertain to the forecasting of weather would be important enough to remember. The others are just for fun.

Isobar…a line representing points of equal atmospheric pressure

Isobath…a line representing points of equal underwater depth

Isobathytherm…a line representing depths of water that have equal temperature

Isochasm…a line representing points of equal recurrence of auroras

Isocheim…a line representing points of equal mean winter temperature

Isochrone…a line representing points of equal time-distance from a point

Isodose…a line representing points of equal radiation intensity

Isodrosotherm…a line representing points of equal dew point

Isogeotherm…a line representing points of equal mean temperature

Isogloss…a line representing points of equal linguistic features

Isogonal…a line representing points of equal magnetic declination or variation

Isohaline…a line representing points of equal salinity in the ocean

Isohel…a line representing points of equal amounts of sunshine

Isohume…a line representing points of equal humidity

Isohyet…a line representing points of equal precipitation

Isoneph…a line representing points of equal amounts of cloud cover

Isopectic…a line representing points of equal ice formation at the same time each fall and winter

Isoplat…a line representing points of equal acidity, as in precipitation

Isopor…a line representing points of equal annual change in magnetic declination

Isostere…a line representing points of equal atmospheric density

Isotac…a line representing points of equal ice melting at the same time each spring

Isotach…a line representing points of equal wind speed

Isothere…a line representing points of equal mean summer temperature

Isotherm…a line representing points of equal temperature

Isorelief…a line representing the point where I’m finally done typing information about “isolines”!

32 points of a compass = 360 degrees

Point of a compass = 11.25 degrees

To convert degrees C. to degrees F., multiply by 9, divide by 5 and add 32

To convert degrees F. to degrees C., deduct 32, multiply by 5 and divide by 9

Inch = 2.54 centimeters

Foot (U.S.) = .3048 meters = 1 British foot

Kilometer = 3,280.8399 feet = .5399568 nm

Statute mile = 5,280 ft = 1.609 km = .869 nm

Nautical mile = 1.15 stat miles = 1,852 m = 6,076.12 ft = about 2,000 yds (generally accepted as 1 minute of latitude)

Length of 1 minute of latitude at equator = approximately 6,046 ft

Length of 1 minute of latitude at poles = approximately 6,108 ft

Knot = 1 nm/hr = 1.15 mph = 1.852 km/hr

Knot-furlong = time it takes to sail 220 yards at 1 nautical mile per hour

Fortnight = 14 days (or nights)

Furlong = 220 yards

Fathom = 6 ft = 1.829 m

Cable = 720 feet = 120 fathoms

Cable (British) = .1 nm

7.5 cables = 1 statute mile

8.44 cables = 1 nm

Charts – nautical miles per inch = reciprocal of natural scale/72,913.39

Charts – statute miles per inch = reciprocal of natural scale/63,360

Charts – inches per nm = 72,913.39 x natural scale

Charts – inches per sm = 63,360 x natural scale

Charts – natural scale = 1:72,913.39 x nm/inch

Charts – natural scale = 1:63,360 x sm/inch

Std. atmospheric pressure at sea level = 29.92126 inches of mercury

Millibar = .02952998 inches of mercury

Millimeter of mercury = 1.3332237 millibars

Register ton = 100 cubic feet

Stone = 14 pounds

Royal firkin = usually 1/4 barrel (varies based on commodity)

Measurement ton = 40 cubic feet = 1 freight ton

Barrel (42 gals) of diesel fuel = 315 pounds

Gallon of engine motor oil = 7.3 pounds

Cubic foot = 7.481 gals of water

Cubic foot of seawater = 64 lbs

Cubic foot of freshwater = 62.428 lbs @39.2 degrees F. (temp. of max. density)

Cubic foot of normal storage ice = 62 lbs

Cubit = the length of the forearm from the elbow to the tip of the middle finger (usually equal to about 18 inches)

Speed of sound is approximately 1,117 feet per second

Approximate distance (nm) of a flash of light to resulting sound = elapsed time divided by 5.5

Displacement ton = 35 cubic feet of seawater = 1 long ton

1 ton of freshwater=35.84 cubic feet

(Note: some values above are based upon relationships

enumerated in Bowditch’s American Practical Navigator,

Vol. I, 1984)

And finally, just for the fun of it…

Ratio of an igloo’s circumference to its diameter = Eskimo Pi

2000 pounds of Chinese soup = Won ton

1 millionth of a mouthwash = 1 microscope

Time between slipping on a peel and smacking the pavement = 1 bananosecond

Weight an evangelist carries with God = 1 billi-gram

16.5 feet in the Twilight Zone = 1 rod serling

Half of a large intestine = 1 semicolon

1000 pains = 1 kilohurtz

Basic unit of laryngitis = 1 hoarsepower

1 million microphones = 1 megaphone

1 million bicycles = 2 megacycles

2000 mockingbirds = two kilomockingbirds

1000 milliliters of wet socks = 1 literhosen

1 millionth of a fish = 1 microfiche

100 rations = 1 C-ration

2 monograms = 1 diagram

8 nickels = 2 paradigms

2.4 statute miles of intravenous surgical tubing at Yale University Hospital = 1 I.V. League