Charts and reference
The tables you actually want on a boat deck, written out in full rather than summarised. Nitrox maximum operating depths, cylinder specifications, wetsuit thickness by water temperature, weighting starting points, hand signals, air consumption by depth and oxygen partial pressures.
- Air Consumption by Depth ChartScuba air consumption by depth: the pressure multiplier at each depth and how long an aluminium 80 lasts at breathing rates from... Open →
- Nitrox MOD Chart: EAN22 to EAN40Nitrox maximum operating depth for every mix from EAN22 to EAN40, in feet and metres, at both the 1.4 ata working limit and the... Open →
- No-Decompression Limits Table (Air)No-decompression limits by depth from the PADI Recreational Dive Planner for air, no repetitive dive, in feet and metres, with... Open →
- Oxygen Partial Pressure Chart (ppO2)Oxygen partial pressure by depth for air, EAN28, EAN32, EAN36 and EAN40, with the 1.4 ata limit, the 1.6 ata ceiling and the NOAA... Open →
- Scuba Hand Signals ChartThe standard recreational scuba hand signals: OK, up, down, stop, low on air, out of air, share air, danger, cold, cramp and the... Open →
- Scuba Tank Specifications ChartScuba cylinder capacity, service pressure, gas per 100 psi and buoyancy swing for aluminium 80, 63, 40 and 100 and steel HP100... Open →
- Scuba Weight Chart by Body Weight and SuitScuba weighting by body weight and exposure suit as a percentage grid, with salt versus fresh water and the end of dive weight... Open →
- Wetsuit Thickness Chart by Water TemperatureWetsuit thickness by water temperature in Fahrenheit and Celsius, from rash guard to drysuit, plus the one step warmer rule for... Open →
How should you use these charts?
As a sanity check and as a way to build intuition, not as a planning tool. A diver who knows without looking that EAN32 tops out around 111 feet, that consumption at 99 feet is four times the surface rate, and that a 5 mm suit starts around 8 to 10 percent of body weight in lead, makes better decisions in the water than one who has to look any of it up. That is what these tables are for.
Two of them carry specific caveats worth repeating here. The no-decompression limits vary by agency and by algorithm and are superseded by your own computer. The cylinder buoyancy figures vary by manufacturer, by valve and by whether the cylinder has a boot, so they are quoted as approximate and should be confirmed against the cylinder in front of you.
The three numbers that appear in almost every table
| Constant | Value | Where it shows up |
|---|---|---|
| Sea water per atmosphere | 33 fsw | MOD, EAD, SAC, ppO2, air consumption. Fresh water is 34 fsw |
| Working oxygen partial pressure | 1.4 ata | Every MOD figure on the site. 1.6 ata is a contingency ceiling only |
| Nitrogen fraction in air | 0.79 | The divisor in every equivalent air depth calculation |
From those three, most of the arithmetic on this site follows. Ambient pressure in atmospheres is depth in feet of sea water divided by 33, plus 1. Oxygen partial pressure is the oxygen fraction multiplied by that. Maximum operating depth is 33 multiplied by the maximum ppO2 divided by the oxygen fraction, minus one. The calculators do the same arithmetic and show their working.
The most looked-up numbers on this site
If you came here for one figure, it is probably on this list. Each row links to the chart that holds the full table and the reasoning behind it.
| Question | Answer | Full chart |
|---|---|---|
| How deep can I take EAN32? | 111 ft at 1.4 ata | Nitrox MOD chart |
| How deep can I take EAN36? | 95 ft at 1.4 ata | Nitrox MOD chart |
| What is the no-stop limit at 60 ft on air? | 55 min | No-decompression limits |
| What is the no-stop limit at 100 ft on air? | 20 min | No-decompression limits |
| What wetsuit do I need at 68 F? | 5 mm full plus hood | Wetsuit thickness chart |
| How much does an aluminium 80 actually hold? | 77.4 cu ft at 3,000 psi | Cylinder specifications |
| How much lead in a 5 mm suit? | 8 to 10% of body weight | Weighting chart |
| How much faster do I use gas at 99 ft? | 4x the surface rate | Air consumption by depth |
| What is the ppO2 of EAN32 at 99 ft? | 1.28 ata | Partial pressure chart |
| What is the signal for low on air? | Closed fist to the chest | Hand signals |
Two of those rows carry conditions rather than certainty. The no-stop limits are the PADI Recreational Dive Planner figures for air with no repetitive dive, and they differ from other agencies and from your own computer's algorithm, sometimes substantially. The hand signals vary between operators and regions, which is exactly why the pre-dive briefing exists.
Why publish tables at all when a computer does the work?
Three reasons, and none of them is nostalgia for tables.
- Intuition survives a battery failure. A diver who knows roughly where the no-stop limit sits at 80 feet, and that EAN32 tops out around 111 feet, will notice when a computer or a fill is telling them something wrong. That noticing is the whole point.
- Planning happens before the dive. You choose a mix, a cylinder, a suit thickness and a weighting figure on the surface, hours before a computer has any data to work with. These are the tables that decision is made from.
- Numbers are checkable and prose is not. This audience is trained. A table with the formula printed above it can be verified in thirty seconds, which is a better relationship with a website than trust.
What tables cannot do is model your actual dive. A table prices the whole dive at maximum depth, whereas your computer tracks the multi level profile you really swam and adjusts continuously. On a typical reef dive that difference is worth real minutes, which is why the computer wins every disagreement.