Scuba diving tables help trained divers plan dives by estimating no-decompression limits and, for some tables, tracking nitrogen exposure across repetitive dives. They are not interchangeable charts: use the specific table system taught by your instructor and follow its instructions exactly. This guide explains the concepts, not a substitute for formal dive training or the table itself.
What information do dive tables use?
Most recreational no-decompression tables use depth and time to estimate how much inert gas—mainly nitrogen when breathing air—your body absorbs during a dive. Depending on the table, you may also use a pressure group or other marker to account for residual nitrogen after a previous dive. Some tables include rules for repetitive dives, altitude adjustments, or special conditions.
Do not assume a table uses your age or weight unless its instructions specifically say so. Do not combine numbers from different agencies’ tables, and never improvise a schedule from a generic online example.
How to read a table safely
- Identify the exact table and its units. Check whether depth is in feet or metres and time is in minutes. Confirm that the table is appropriate for your training and planned dive.
- Use the planned maximum depth. Follow the table’s prescribed method for selecting the depth row or column. If your actual dive is deeper than planned, do not simply continue using the shallower entry.
- Check the time limit. Find the table’s permitted exposure or no-decompression limit for the planned depth. The exact steps and labels differ by table system.
- Account for previous dives when required. Use the table’s procedure for residual nitrogen, surface intervals, and repetitive dives. Do not estimate these values from memory.
- Plan a conservative dive and follow your training. Leave a margin for changing conditions and end the dive according to your plan, gas supply, buddy agreement, and training.
Do dive tables tell you when to make decompression stops?
Recreational no-decompression tables are commonly used to plan dives that remain within specified no-decompression limits. They are not a license to plan decompression dives, and the numbers should not be treated as a guaranteed boundary between safe and unsafe diving. Decompression obligations depend on the complete dive profile and the planning method being used.
Tables versus dive computers
A dive computer tracks depth and time during the dive and calculates information using its programmed model. It does not remove the need to plan, monitor gas, control buoyancy, dive within training, and follow the manufacturer’s instructions. If you use tables, learn their method in a recognized course. If you use a computer, understand its settings and limitations and do not switch between planning systems casually during a dive.
Common mistakes to avoid
- Using a table from a different training system without understanding its method.
- Confusing bottom time, total dive time, and surface interval.
- Ignoring repetitive-dive or altitude procedures when they apply.
- Assuming that a table guarantees a dive will be free of decompression illness.
- Using a generic internet example as a real dive plan.
Where to learn more
Learn table use with a qualified instructor and the official materials for your training agency. For additional safety guidance, see Divers Alert Network’s safe-diving practices. Follow the current training materials and do not use this article to calculate an actual dive.
Key takeaway: Dive tables are planning tools that must be used as designed. If you are uncertain about a row, pressure group, or repetitive-dive calculation, pause and ask your instructor rather than guessing.
Planning with scuba dive tables: details beginners should understand
A dive table represents a model rather than a direct measurement of gas in your tissues. It is built around defined assumptions, so divers must follow the complete procedure taught in training. Depth changes, elapsed time, surface intervals, and previous dives can all affect a plan. Write down the planned profile and review it with your buddy before entering the water instead of working out calculations at the last minute.
How to practise reading dive tables
Practise with fictional scenarios from your course materials: identify the correct depth, find the applicable time limit, and explain how the table treats a repetitive dive. Check every answer against the official instructions. If a planned depth falls between listed values, use the conservative method specified by that table; never invent your own rounding rule. Ask an instructor to check any step you cannot explain confidently.
When a dive plan needs to change
If conditions, gas supply, current, visibility, or your buddy’s comfort differ from the plan, respond conservatively and follow your training. A table cannot account for every individual factor or guarantee that decompression illness will not occur. Use it only for the type of diving for which you are trained, and seek instructor guidance about altitude, repetitive dives, or other special procedures.