Conversion Factors

Useful Relationships, Formulas, & Laws for

Scuba Divers
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LENGTH:

1 inch = 2.54 centimeters = 0.0139 fathoms

1 foot = 0.3048 meters = 0.1667 fathoms

1 yard = 3 ft = 0.9144 meters = 0.5 fathoms

1 fathom = 6 ft = 2 yards = 1.8288 meters = 0.0003289 leagues

1 statute mile = 5280 ft = 880 fathoms = 1.609 km = 0.2895 leagues

1 nautical mile = 6080 ft = 1013.3 fathoms = 1.853 km = 0.33 leagues

1 league = 18240 ft = 3040 fathoms = 3.45 statute miles = 3 nautical miles

WEIGHT and VOLUME:

salt water: 1 cubic foot = 64 lbs = 28.317 liters = 7.481 gals

1 gal = 8.555 lbs = 3.786 liters = 0.1337 cubic feet

fresh water: 1 cubic foot = 62.4 lbs = 28.317 liters = 7.481 gals

1 gal = 8.341 lbs = 3.786 liters = 0.1337 cubic feet

An 80cu.ft. SCUBA tank weighs 5 pounds (approx. 4 - 6) less empty than when pressurized at 3200 psi

PRESSURE:

1 atm = 14.7 psi = 1.03 kilograms per square centimeter = 1 bar

1 deg F makes a 5 psi (approx.) change in pressure in a SCUBA tank.

Airplane cabin pressure @ 30,000 ft = atm @ 8000 ft = 10.5 psi (approx.)

In salt water: (Depth in feet)

atm = Depth / 33

ata = (Depth / 33) + 1

psi = Depth x 0.445

psia = (Depth x 0.445) + 14.7

In fresh water: (Depth in feet)

atm = Depth / 34

ata = (Depth / 34) + 1

psi = Depth x 0.432

psia = (Depth x 0.432) + 14.7

CONSTANTS:

Sound travels 4 times faster in water than in air.

Water is 800 times (approx.770 - 800) more dense than air.

Objects appear 25% larger through a mask in water than in air.

Light Absorption order: red, orange, yellow, green, blue, indigo, violet.

Body heat is lost 20 times (approx. 20 - 25) faster in water than in air.

As much as 75% of body heat lost may be from a diver's head.

Carbon monoxide bonds 200 times easier with hemoglobin than O2.

Exhaled breaths of air contain 16% O2 (approx.).

ENRICHED AIR NITROX: (Depth in feet)

Equivalent Air Depth = ((1 - O2%) x (Depth + 33) / 0.79) - 33

O2 Partial Pressure = (Depth + 33) / 33 x O2%

Maximum Depth Limit = (46.2 / O2%) - 33

Contingency Depth Limit = (52.8 / O2%) - 33

Maximum P.P. O2 = 1.4 ata

Contingency P.P. O2 = 1.6 ata

NOAA Nitrox I = EANx 32

NOAA Nitrox II = EANx 36

SPEED:

1 kph = 0.912 fps = 0.622 mph = 0.539 knots

1 fps = 1.096 kph = 0.682 mph = 0.592 knots

1 mph = 1.609 kph = 1.467 fps = 0.868 knots

1 knot = 1.854 kph = 1.689 fps = 1.152 mph

TEMPERATURE:

deg F = (C x 1.8) + 32 deg

deg C = (F - 32) / 1.8 deg

TIME:

1 fortnight = 14 days = 2 weeks = 0.7 score = 0.46 months = 0.038 years

1 score = 20 days = 2.85 weeks = 1.42 fortnights = 0.66 months = 0.054 years

1 month = 30 days = 4.28 weeks = 2.14 fortnights = 1.5 score = 0.082 years

1 year = 365 days = 52.14 weeks = 26.07 fortnights = 18.25 score = 12.16 months

RULES

The most important rule of SCUBA diving: Breathe continuously, never hold your breath.

Bill Jones' second rule of SCUBA diving: The guy closest to you with air is your buddy.

Murphy's third corollary: Things tend to go wrong all at once.

O'Toole's commentary: Murphy was an optimist.

I. J. O'Toole lived a secluded life in a basement apartment, afraid of everything. He was afraid to go outside and face the dangers of everyday living. In spite of his careful avoidance of interacting with others, he died prematurely in bed of natural causes. Before his death, he wrote: "My greatest fear is that I won't know the difference between my death and the life that I have led".