Gas needed answers will my cylinder last this dive? It works out the gas you breathe at one depth for a set time and takes it from your cylinder. It is a quick check of a stretch of diving, not a gas plan.

What you enter

• Depth (m) and Time (min): the stretch of dive, held at that depth throughout.
• RMV (L/min): your surface-equivalent breathing rate. Measure it with RMV from a dive.
• Water: Salt or Fresh.
• Size, each (L), Start (bar) and Cylinders (Single or Twin): your cylinder. Twin doubles the gas at the same pressure.

The Breathing and Cylinder fields are shared with Turn pressure and Minimum gas, so a change here shows there too.

Reading the result

• Gas needed (L): the main figure. Its rail shows the pressure used against a solid mark at your full Start pressure, and turns red when the dive needs more than the cylinder holds.
• Pressure used (bar): the same gas as a gauge drop.
• Left (bar) and Left (%): what the gauge reads at the end. The bar figure turns red when it goes below zero.

With gas to spare, the verdict reads, for example, Leaves 108 bar. Check that covers your ascent and reserve with Minimum gas. Without, it reads Not enough gas, with what the dive needs and what the cylinder holds.

What it leaves out

The method note says it plainly: this is gas breathed at one constant depth for the whole time.

• No descent, ascent or stops. The gas to get down and back up is not counted.
• No reserve. Gas left at the end is not gas you can spend. Work out what to keep with Minimum gas.
• No stress. The RMV is your relaxed rate throughout.

For a whole dive, with every level, stop and gas, build a plan in the planner.

Next

• Turn pressure sets when to end the outbound leg.
• Gas use in a plan covers the same question for a whole dive.