Some common formulas

Here are some common formulas. For those tec's out there, this is old stuff.
I post for the reference as well as for those who are curious. For the more
seasoned diver who if itchy to learn more about the physics of diving, this
will help out too. Look up the achronym online, ie END or MOD, SAC, TGC
(on how to calculate TGC), etc... to get a better idea of what and why. Of
course, get training as a Advanced Nitrox and/or Trimix diver to learn more.

As one becomes more techical, computers are good, but planning is important.
Computer programs available for purchase will help, but when you're out in the
field and there is not computer, knowing the formulas will come in handy.

This is not a comprehensive list of formulas, just some I choose to write
down. Why these particular formulas? Because they are the ones that came
to mind when writing this post.

EAD: Equivalent Air Depth
D: Depth
T: Time
TGC: Total Gas Consumed
FO: Fraction of Oxygen
TOD: Target Operating Depth
MOD: Maximum Operating Depth
END: Equivalent Nitrogen Depth
tEND: Target END
SAC: Surface Air Consumption
RMV: Respiratory Minute Volume
RCWP: Rated Cylinder Working Pressure
RCV: Rated Cylinder Volume
EAD: Equivalent Air Depth
FN: Fraction of Nitrogen
PO2: -or- PPO: Partial Pressure of Oxygen

FN = (EAD + 33) * .79 / (D + 33)

FO = PO2 / (( D / 33 ) + 1)
ie. FO = 1.4 / (( 132 / 33 ) + 1

TOD = (( PO2 / FO2 ) - 1 ) * 33
ie. TOD = (( 1.4 / .32 ) - 1 ) * 33

MOD = (( PO2 / FO2 ) - 1 ) * 33
ie. MOD = (( 1.6 / .32 ) - 1 ) * 33

END = ((tEND + 33) * .79) / ( D + 33)

SAC = TGC / ( D * T )

RMV = (( SAC / RCWP / RCV ))

EAD = ((( FN * ( D + 33 )) / .79 ) - 33

I'll post more later....

Good stuff!

Lars, when you post more we'll edit your original post to add them all together, thanks for the info.

Safety is first thing for divers, you can go with the most of the instructions followed by professional divers, learn everything before going to start diving.