Understanding the ACA Canyon Rating System
Understanding the ACA Canyon Rating System
If you’re new to canyoneering, or you’re looking at one of our guided trips and wondering what kind of ability, gear, or experience level a route calls for, the canyon rating system is the fastest way to get a rough read on what you’re signing up for. Several regions around the world use their own rating conventions. This post covers the system developed by the American Canyoneering Association (ACA), the standard used for canyoneering routes across the United States.
Where the Rating System Came From
The ACA was founded in 1999 by Rich Carlson, shortly after he became the first American certified as a canyoning guide in Europe. Carlson — known to a lot of longtime Canyoneers as the “Godfather” of the American side of the sport — drew on European canyoning rating conventions, including work by Stefan Hofmann, as a starting point for something built specifically for U.S. canyons. In May 2000, the ACA launched the “Canyons Group,” the first online canyoneering discussion forum in the country. Over the following year or two, Carlson and that early community worked through the rating system in public, iterating until it reached something close to consensus. It’s been the standard reference used in guidebooks and route descriptions across North America ever since — credit for the system itself belongs to the ACA.
How to Read a Rating
A full ACA rating looks something like 4BIV. Three separate pieces of information get packed into that string:
- 4 — Technical Rating (rope work and terrain difficulty)
- B — Water Volume/Current
- IV — Time Commitment
Here’s what each one actually means.
Technical Rating (1–4)
This number tells you how much rope work, climbing, and technical skill the canyon demands.
1 — Canyon Hiking. No rope needed. You might use your hands for balance on some easy scrambling, but you can travel the canyon in either direction without technical gear.
2 — Basic Canyoneering. Expect more scrambling and some easy down-climbing that requires hands more often. A rope is a good idea here — for hand lines, belays, lowering packs, or an emergency — even though it isn’t strictly required. Like a 1, you can still travel up or down the canyon, just with more effort.
3 — Intermediate Canyoneering. This is where rappelling becomes the norm. Down-climbing gets difficult enough that most groups will just rappel instead, and a rope is required for belays and single-pitch rappels. You’re building and evaluating your own anchors here — natural or fixed — and if you need to retreat back up canyon, you’ll be ascending fixed rope left in place. Basic pothole-escape skills, like partner assists and counterweights, may come into play.
4 — Advanced Canyoneering. Any combination of: difficult, exposed free climbing or down-climbing; aid climbing; multi-pitch rappels; complex rigging (guided rappels, deviations, rebelays); anchors that are obscure or poorly defined; advanced problem-solving and anchor-building; serious pothole work around keeper potholes; long swims; or extended high-angle scrambling and stemming.
Water Volume/Current (A–C)
The letter tells you what kind of water you should expect.
A — Typically dry, or close to it. You might hit a dry fall or two. Any water present is usually shallow enough to avoid or walk through without swimming. Shoes might get wet; a wetsuit or drysuit shouldn’t be necessary.
B — Water is normally present, but it’s still or barely moving — pools and potholes rather than current. Falls tend to be dry or reduced to a trickle. Plan on some wading or swimming, and depending on air and water temperature, a wetsuit or drysuit may be worth bringing.
C — Water with current, usually with waterfalls to go along with it. Expect real wading and swimming against or through moving water and pack thermal protection accordingly. Because “current” covers a lot of ground, Class C sometimes gets broken down further:
- C1 — Light to moderate current; hazards are manageable.
- C2 — Strong current; features like hydraulics or siphons start to require real swift water skill.
- C3 — Very strong current; dangerous hazards, experts only.
- C4 — Extreme hazards that are hard to manage even for strong, experienced swimmers.
In practice, you’ll rarely see this subdivision applied around here. It’s built for canyons with genuine flowing currents, the kind of hydraulics and siphon hazards you find in river-fed or flash-flood-prone terrain elsewhere in the Southwest. Every canyon we run in North Wash, Cedar Mesa, and Capitol Reef tops out at Class B — still water, not current — so the C1–C4 breakdown doesn’t come into play in our desert canyoneering.
Worth remembering; water levels move around a lot — year to year, season to season, even day to day. If you show up and the water’s running noticeably higher than the rating suggests, the descent will be harder than the route description implies. That’s the moment to stop and reassess, not push ahead on the strength of a rating you read online months earlier.
Time Commitment (I–VI)
This tells you roughly how long the canyon takes, though group size and experience level swing it around more than people expect.
- I — A couple of hours, tops.
- II — Roughly half a day.
- III — A full day out — out after breakfast, back by dinner.
- IV — A long day. Start early, expect to finish in the dark, bring a headlamp for both ends.
- V — Overnight. Bring bivy gear, extra food, and extra water.
- VI — Multi-day, two nights or more. Pack and plan accordingly.
That’s the core system — the same three-part structure that’s been the backbone of American canyon ratings for over two decades. It’s meant to give you a starting baseline, not a guarantee. Conditions shift with the seasons, so it’s always worth checking current beta before you commit to a trip.
What Else You Might See Tacked On
Beyond the base rating, two more pieces of shorthand show up often enough that you should know them.
Climbing Grades (YDS)
Some canyons include a move — usually on the exit — that’s rated using the Yosemite Decimal System, the same scale used for rock climbing (5.6, 5.8, and so on). This usually shows up when the only way out of a canyon involves a climbing move, and typically one person in the group free-climbs it first to set a rope for everyone else. As a rule of thumb, anything under 5.0 is considered doable without a rope; above that, a fall carries real injury risk and a rope is expected.
I’ve been on the wrong end of one of these firsthand — got about halfway up an exit climb and simply ran out of reach and leg length to finish it. We got another member of the group up to me so I could spot them. They were then able to finish the climb where they set a rope I used to finish the climb up and help the rest of the group out behind us. A YDS number on a canyon exit isn’t a footnote — plan for it.
Risk/Seriousness Rating (G, PG, R, X, XX)
This is a separate layer on top of the technical rating, meant to flag when a canyon carries risk beyond what its base number would suggest.
G — General audience. Should be straightforward for anyone who already has the skills the base rating calls for.
PG — Competent leadership matters here. Beginners can usually get through with solid guidance, as long as they can stay calm and think clearly under a bit of stress — tight spaces and heights can be a real problem for some people, rating or no rating.
R — Risky. One or more factors push this canyon past a normal experience for its class — tight squeezes, awkward high stemming, or rappels that demand extra rigging knowledge. Not a beginner canyon.
X — Extreme. Multiple risk factors stack up here. This canyon calls for competent leadership and well-practiced skills — no beginners, no exceptions.
XX — Double Extreme. About as serious as the rating system gets. Solid skills and real experience required, full stop.
Two things worth remembering about this rating: its presence is a genuine warning, but its absence doesn’t mean a canyon is risk-free — canyoneering carries inherent risk at every level. Factors that typically drive one of these ratings include the number and length of rappels, how exposed the terrain is, anchor quality and availability, how hard the canyon is to navigate, flash flood exposure, how easy or difficult it would be to exit or get help, water temperature, and how long you’d be immersed in cold water if something went wrong. A good route description should spell out which of these actually apply.
How This Plays Out on Our Trips
Here’s how a few canyons you might guide with us — or have heard of — actually break down under this system.
Leprechaun Canyon: There are three forks, and the rating gets a little more interesting once you look past the base number. All three forks start at 3BII. The Middle Fork picks up an R- (a minus, so it sits between a PG and a full R). The right fork — the one we guide — stays a straightforward 3BII with nothing added on.
Blarney Canyon: A straightforward 3AI. No added risk rating — straightforward rappels and down-climbing.
Hogwarts Canyon: Also 3AI, but with a few more rappels than Leprechaun or Blarney, and they run higher and feel more exposed. The rappels demand more attention to rigging detail.
Miss Piggy Canyon: Our newest addition, rated 3AII. It has a couple of narrow sections, longer rappels, and a climber’s exit. The exit doesn’t carry a formal YDS rating in the beta we have, but it sits around the low 5.0s to mid-4s — steep, but not seriously exposed.
A few you might already know from hiking on your own, without a guide or technical gear:
- Leprechaun (lower section): a short stretch you can walk in from the car and back out, rated 1AI — about an hour round trip with a few easy up-climbs.
- Spooky and Peekaboo: run 2AI to 2AII depending on how you loop them together.
- Zebra Canyon:
- Little Wild Horse Canyon: 1A/BII/III, depending on the loop and time of year.
Ratings like these can get subjective, and it’s worth understanding how the pieces fit together rather than just reading the final string. Use them as a starting filter, then dig into the actual route description for the specifics.
The Rating Is a Starting Point, Not the Whole Picture
Two experienced beta writers can land on slightly different numbers for the same canyon, especially on judgment calls like water class or risk designation. Treat the rating as your first filter, not your only source. Look up current route descriptions, check recent trip reports, and don’t hesitate to ask in the Facebook and Reddit groups where people post real-time conditions.
And whatever the rating says: check the weather forecast before you head into a slot canyon. Flash floods don’t care what class a canyon carries.
If you’re weighing which of our trips fit your experience level, reach out — we’re happy to help you find the right one. And if you’ve worked your way through everything we currently offer, ask us what else we can put together that isn’t on the booking list. We’ll see you out in the canyons.
Guided Canyoneering Trips:
https://www.northwashoutfitters.com/canyoneering-trips/