# Diving Buddy Calculators

### Maximum Operating Depth

The maximum operating depth (MOD) of a breathing gas is the depth below which the partial pressure of Oxygen (ppO2) of the gas mix exceeds a safe limit.

This safe limit is somewhat arbitrary, and varies depending on the diver training agency or Code of Practice, the level of underwater exertion planned and the planned duration of the dive

### Minimum Cylinder Pressure for Ascent

Calculate how much gas is required to get from the depth at which you begin your ascent to the water's surface. The result will include a reserve gas value, which will be either 1/3 of your starting gas, or 1.5 times the gas required for ascent.

### Run Time

Determine how long your dive can last. Every trained diver knows that as you go deeper you use more air, and so you cannot stay as long.

The "run time" of a dive is the number of minutes from leaving the surface until leaving the bottom for an ascent to the surface.

In this particular model, the reserve is fixed at 1/3 of the starting gas or 1.5 times the gas required for the ascent, and stops whichever is the greater.

### Weight Required

The amount of weight that needs to be added is dependent on a number of factors:

- Your suit type
- The cylinder type you are using
- Whether you are in fresh or salt water
- Your bodyweight

Any of these will alter how much weight you need to add (or possibly take away!). This is not an exact science, but the Weight Calculator will provide a really close estimate.

NOTE: The calculation has been tested for standard singles (12 litre/0.43 cubic feet) only. You can select either Aluminium or Steel for this.

### Weight of Air in Cylinder

The weight of air in a cylinder is determined by two factors:

- Cylinder size
- Cylinder pressure

The weight of the air - as well as the volume - can then be calculated. This can be useful for working out how much extra weight to add or take off.

### BSAC Oxygen Toxicity

Calculate your doses of Oxygen Toxicity when diving with Nitrox. The results from this calculator will be the Unit Pulmonary Toxicity Dose (UPTD) and %Central Nervous System (%CNS).

Although you can calculate your Oxygen Toxicity on a dive-by-dive basis, you can also link dives together for when you dive multiples times in the same day. You create the individual Oxygen Toxicity calculations, and enter the interval in hours between the dives. The calculator will then determine the aggregate UPTD and CNS values.

### Balancing Air Between Cylinders

Given the size and pressure of two different cylinders, this calculator will determine the pressure that will be in each cylinder after the air has been balanced. Works with cylinders of different sizes.