TDI Equivalent Ratings with other Scuba Diving Agencies

by Jon Kieren:

A few months ago, we released an article that broke down all of the SDI Diver certifications and what the most popular agency equivalent ratings were.  You can view this article HERE.  The goal of posting that equivalency chart was to provide a resource for divers and dive professionals to help navigate the web of diver certifications.

This has been a popular blog post that has proven to be a valuable resource, and we have received many requests to create a similar page for TDI ratings.  First impression would be that this should be fairly straight forward, however when you look a bit deeper, you will quickly see the challenges it presents.

Not all Scuba Diving Agencies are Created Equal

First and foremost, not all technical diver ratings are created equal.  Every training agency takes a different approach when it comes to the flow path for creating technical divers.  Throw in helium, rebreathers, cave diving, sidemount, etc. and the flow path begins to look more like a tangled complicated web of options.  And that’s just for each agency; now imagine crossing back and forth from one agency to the next, and it becomes a nearly unmanageable maze.  But we’re going to try to break it down for you here.

Before we get into the different ratings from different agencies, it’s important to discuss the philosophies TDI holds for all technical diver training.  One of those philosophies is based on prerequisites.  If you are unfamiliar with this aspect of TDI’s training flow path, please reference the article recently posted regarding prerequisites HERE.  Aside from prerequisites, TDI also strongly believes that each course should be focused on one specific aspect of diving.  Whether it’s a new piece of equipment (i.e. a rebreather) and environment (i.e. a cave), OR extending the diver’s range (depth, distance, decompression obligation) for that specific piece of equipment or environment.  These aspects are NEVER combined into a single course.

For example, if you are not a trained decompression diver, your first rebreather course will not qualify you to conduct decompression dives using that rebreather.  You will have to complete the entry level rebreather course, get some experience on the unit, then take a CCR decompression diver course (Air Diluent Decompression or Helitrox Decompression).  This ensures the student is focused on developing critical equipment related skills in an environment and conditions that they are already very comfortable with.  The requirements and prerequisites for each situation (depth, decompression, and overhead environments) are clearly defined in the TDI Standards and Procedures.

Not all agencies hold these same beliefs in their training programs, which effects where they fall in accordance with TDI certifications.  When determining equivalencies, there are several factors that are considered:

  • What does the certification qualify a diver to do (equipment, depth, decompression, gasses, and environment)?
  • What has it taken to get the diver to that level of certification (prerequisites, course completion requirements)?
  • What does it take to become an instructor at that level (would the instructor teaching the course meet the requirements to become a TDI instructor for an equivalent rating)?
  • What does it take to become an instructor trainer at that level (would the instructor teaching the course meet the requirements to become a TDI instructor trainer for an equivalent rating)?

Based on which of these requirements are equal to the TDI rating, we may consider a diver certification equivalent.  Here’s how we break it down:

Open Circuit: Non-overhead »

Closed Circuit: Non-overhead »

Open Circuit: Cavern and Cave »

Closed Circuit: Cavern and Cave »

Compare open circuit-non overhead diver course equivalencies with this chart:

NitroxRec 2NitroxNitroxNitrox
Advanced Nitrox- 40 meters/130 feet, up to 100% O2, No DecompressionRec 3Advanced NitroxTec 40Extended Range Nitrox
Decompression Procedures- 45 metres/150 feet, air/nitrox bottom gasTech 1Technical DiverTec 45Extended Range
Helitrox- 45 metres/150 feet, unlimited decompression, Helitrox bottom gas (min 21% o2, max 20% helium)Tech 1Advanced Recreational TrimixTmx 50Extended Range Trimix
Extended Range-55 metres/180 feet, unlimited decompression, air/nitrox bottom gasTech 1Technical DiverTec 50Technical Extended Range
Trimix- 60 metres/200 feet, unlimited decompression, trimix bottom gas (min 18% o2)Tech 60Normoxic TrimixTmx 65Technical Extended Range
Advanced Trimix- 100 metres/330 feet, unlimited decompression, hypoxic (less than 18%O2) trimix bottom gasTec 3TrimixTec TrimixHypoxic Trimix

*Note – Recommendation for all TDI courses – Any new student should demonstrate skills required in previous courses to the new instructor in shallow water.

If you do not see your dive training organization on this list and you are curious if it’s equivalent to an SDI, TDI, or ERDI rating, let us know!  Simply write a message to the training department ( and we will be happy to help.

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15 replies
  1. Joshua Hill
    Joshua Hill says:

    Too bad the other big agency wasn’t included. A comparison between TDI and NAUI would have been much more useful than a TDI to SSI or TDI to ANDI comparison.

    • Jon Kieren
      Jon Kieren says:

      Hi Joshua,
      Thanks for the input. The agencies listed were chosen purely out of the volume of inquiries we receive on a global scale.

  2. Lisa Goodlin
    Lisa Goodlin says:

    GUE training is so different from that of other dive training organizations that I’m not sure it even makes sense to include it in the charts. For instance, Nitrox is used from the start in Rec 1 (GUE’s open water class). Decompression procedures in the form of minimum deco are also introduced in Rec 1. TDI Advanced Nitrox, which I took several years ago, does not have much in common with Rec 3 which I am taking now. Helium is used in Rec 2 and Rec 3 as well as Tech 1 and higher.

  3. Jon Kieren
    Jon Kieren says:

    Hi Lisa,

    You are correct, the flow path for GUE divers is very different than many agencies. However, we see a high volume inquiries coming in from GUE divers wishing to take TDI courses, and we feel it is important to give them as much credit as we can for the work they have completed already. The article above explains why this can be difficult, and the charts are intended to show how a diver coming from another agency may fit into the TDI curriculum.

    While some of the qualifications of a GUE Rec 3 diver may be higher than that of a TDI Advanced Nitrox diver (use of helium for example), they have restrictions that a TDI Decompression Procedures diver does not (i.e. depth and limited decompression). So while that rating may seem to exceed the TDI Advanced Nitrox rating, it would not cover the TDI Decompression Procedures requirement as a prerequisite to enter higher level courses such as TDI Trimix.

    We greatly appreciate the feedback, please let us know if there is anything we can do for you.

    • Jose Duarte
      Jose Duarte says:

      Hi Jon,

      A well achieved GUE diver will have difficulties on making a decision to take any other agency courses…

      However, I’ve been seen over the years divers that fail to move up the GUE ranks (by inability most of them, but some by other restrictions) taking another path to reach a “depth” goal – opposing the ethos and objectives of GUE. Not saying that the other agencies courses are easier, but just that I’ve noticed this movement over the years with some GUE divers that either failed Fundies, Tec1 or achieving a Tec pass in Fundies.

      Would be interesting if agencies could cooperate more closely to make sure everyone has the right understanding of what courses aims to achieve, passing criteria, standards, ratios of quality among instructors, etc., inter-agency.

      I’ve seen people saying “you should chose the instructor rather than the agency”, which I tend to agree for some agencies but not all… The agency should/must ensure its instructors quality and standards, failing to do so divers have huge problems taking the right courses to achieve their diving objectives. This table seems to make it even more complicated.

      By your comment, I seem to understand the criteria, i.e. numbers and “features/skills”… Also, I do understand that putting something like this together may be highly complex, as I believe passing criteria, instructor quality ranking ratios, etc., should be considered. However if some cannot achieve that, in my humble opinion/view one should not develop such lightly minded comparison.


  4. Luc Pols
    Luc Pols says:

    This chart’s usefulness without NAUI is very limiting. I question the logic why they weren’t included. They are the second largest dive agency out there. I find the reason that they were excluded was due to global response is insufficient. To omit NAUI seems like a massive oversight.

  5. Pmnc
    Pmnc says:

    I have my dive master cert from SDI but Padi doesn’t recognize it. If I want to be a dive master at Padi I have to take the Padi course. The SDI shop in my area closed so the next closest shop is Padi. Anyone have any idea’s?

  6. Paul
    Paul says:

    I have my DM from SDI, the shop I was working for closed and the next closest shop is a PADI shop. When I went there I was told that PADI doesn’t recognize the SDI DM cert. If I want to be a PADI DM I have to take the PADI course. Is there really that much difference between an SDI DM and a PADI DM?

  7. De Bruyne Alain
    De Bruyne Alain says:

    hi ,pmnc and paul, your statement is not intiarely correct, your DM rating from SDI is recognized by Padi buth not to act as a divemaster, you can however step up in an Padi IDC course to become a padi instructor, thr reason why you cannot have the same rating is for differences in standarts.

  8. Dave Sutton
    Dave Sutton says:

    Interesting that the originator of all civilian NITROX training worldwide and the only major training agency with zero reportable accidents during training in its entire existence (ANDI) was not included. It does a disservice to not show ANDI students how they might enter the TDI flow (and vice versa).


    Do you know about CMAS certification ? I am Instructor 2 stars with CMAS. Dove may be 100 time at 60 m, used decompression protocol with MN90 table and dive computer ! Do we have any equivalent ? Thank for all answer.

  10. Christopher Painter
    Christopher Painter says:

    As a GUE, IANTD and PADI certified diver I know enough about many of these classes to know that the table of equivalencies should be taken with a massive grain of salt. I won’t go into details because that’s seeing the trees not the forest. I’m at a point where there are no instructors around me to continue my training with IANTD or GUE and there are few TDI or PADI instructors around me and none of them really know me as a diver. I don’t want to come across as a card collector trying to skip a level and I don’t want to go back and repeat a level doing stuff I already know. Regarding the GUE Rec 3 and IANTD Advanced Nitrox vs TDI Advanced Nitrox, I don’t think I can agree. There are some limits placed on these cards but both of those divers are doing accelerated decompression dives that is far in excess of TDI AN or PADI Tec 40. Another way to look at it is that IANTD allows an AN diver to take Normoxic Trimix next. TDI would have you go back and take deco procedures. I would hope that it’s possible to get evaluated by a TDI instructor and if suitable skip deco procedures or take a very short version of it (to brief any differences in protocols/procedures) and then proceed on to Trimix or Helitrox if desired (which I think is comparable to IANTD Advanced Recreational Trimix ).

    I don’t really see this as a problem at the recreational level classes. With the exception of Master Diver meaning one thing to NAUI and something else to almost everyone else an OW, AOW, Rescue diver is clearly understood and transferable.


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