Join DiveBuddy.com

Meet new scuba divers, maintain a virtual dive log, participate in our forum, share underwater photos, research dive sites and more. Members login here.

Diving Formulas
Kirkpfeil - 5/17/2007 12:00 AM
View Member Articles
Category: Educational
Comments: 2
Here are some formula`s that I hope you all find as useful as I did. If you have any that you want to add, please do, it`s great for a referance library.

Useful Relationships, Formulas, & Laws for Scuba Divers

LENGTH:
1 inch 2.54 centimeters 0.0 139 fathoms
1 foot 0.3048 meters 0.1667 fathoms
1 yard 3 ft 0.9 144 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 7.48 1 gals
1 gal — 8.555 lbs — 3.786 liters — 0.1337 cubic feet
fresh water: 1 cubic foot 62.4 lbs 28.3 17 liters 7.481 gals
1 gal 8.341 lbs 3.786 liters 0.1337 cubic feet
80 cu.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 fret)
atm Depth/33
ata (Depth / 33) + 1
psi Depth x 0.445
psia (Depth x 0.445) + 14.7

In fresh water: (Depth in fret)
atm Depth/34
ata (Depth / 34) + 1
psi Depth x 0.43 2
psia (Depth x 0.43 2) + 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% 02 (approx.).

ENRICHED AIR NITROX: (Depth in feet)
Equivalent Air Depth ((1 - 02%) x (Depth + 33) / 0.79) - 33
02 Partial Pressure (Depth + 33) / 33 x 02%
Maximum Depth Limit (46.2 / 02%) - 33
Contingency Depth Limit (52.8 / 02%) - 33
Maximum P.P. 02 1.4 ata
Contingency P.P. 02 1.6 ata
NOAA Nitrox I EANx 32
NOAA Nitrox II EANx 36

SPEED:
1 kph 0.9 12 fps 0.622 mph 0.539 knots
1 fps 1.096 kph 0.682 mph 0.592 knots
1 mph 1.609kph 1.467 fps0.868 knots
1 knot 1.854kph 1.689fps 1.152mph

TEMPERATURE:
degF(Cx 1.8)+32deg
deg C (F - 32) / 1.8 deg

TIME:
1 fortnight 14 days 2 weeks 0.7 score 0.46 months 0.038 years
score 20 days 2.85 weeks 1.42 fortnights 0.66 months 0.054 years
month 30 days 4.28 weeks 2.14 fortnights 1.5 score 0.082 years
year 365 days 52.14 weeks 26.07 fortnights 18.25 score 12.16 months

Thanks,

Kirk

Comments

Dorkfish - 5/18/2007 12:00 AM
80 cu.ft. SCUBA tank weighs 5 pounds (‘approx. 4 - 6,) less empty than when pressurized at 3200 psi

It is very important that each diver know his/her equipment. The above measurement for 80cf tanks will vary by manufacturer (but not by much) but more specifically by model. For example: Luxfer makes it`s 80cf tanks in 80S and 80N models. The 80N tank is slightly negative, thus it is slightly heavier both empty and full.

This is vital information for those who might need to adjust their weighting from pool/fresh water to salt water. 1 or 2 pounds makes all the difference in some cases, especially if it`s your tank.
Greg - 5/17/2007 12:00 AM
Wow, thanks for the info. I edited your blog and added some html to make it look nice.