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When you stand under a crack, the first question is how wide it is. Width decides whether you jam fingers, a hand, a fist or a whole arm. Change the size and you're almost doing a different sport.
This series is for people who have read the crack-climbing primer. That post covered the five shared rules of jamming and the idea behind each size. This series takes each size apart, one post each, until the jam really holds your body weight. Every post comes with videos from 2020 or later, from different crags and different people: pro climbers, guides, people new to cracks, and climbers with very big and very small hands.
This post is the map. By the end you should be able to look at a crack, say roughly which size it is and which post to read, and understand why a friend finds a crack easy that you can't get up.
Eight sizes, from fingertips to your whole body
From narrow to wide, cracks fall into roughly eight sizes. Each uses a different part of the body. Topos usually describe width by which cams to bring, so the table also lists rough sizes (Black Diamond's Camalot range, for a medium hand):
| Size | What you jam | Rough cam size | What it feels like | In this series |
|---|---|---|---|---|
| Tips | Only fingertips or the first joint fit | Below 0.3 | The most painful and hardest; often needs feet and laybacking | Finger cracks |
| Fingers | Fingers to the second or third knuckle, twisted to lock | 0.3–0.5 | Very sensitive to finger size; one millimetre changes everything | Finger cracks |
| Off-fingers | Ring locks, fingers and thumb stacked | 0.5–0.75 | The awkward size: fingers rattle, the hand won't go in | Off-fingers |
| Hands | The whole hand to the wrist, thumb tucked to expand | 0.75–2 | The most secure; most people learn it first | Hand cracks |
| Fists | A clenched fist | 3–4 | Little room to expand, often feels insecure | Fist cracks |
| Offwidth | Arms, shoulders, knees, stacked hands | 4–6 | From "my hand is stuck" to "my whole body is stuck" | Offwidths |
| Squeeze | Body sideways, braced with shoulders and hips | 6 and up | You fit in but can't turn around | Squeezes and chimneys |
| Chimney | Back on one wall, feet on the other | Often no cam fits the main crack | No longer jamming, but bridging | Squeezes and chimneys |
The cam column is this post's rough placement, based on Pete Whittaker's comparison in the next section. Big or small hands shift every row a step or two either way, as the next section explains.
Kim Jong-sik, a Korean climbing guide and a founding figure of the Korean climbing-guide association KMGA, draws the line with the thumb in the first lesson of his course: if your thumb goes in past its third knuckle, it's a hand crack. He also points out that width is only one part of difficulty. A flaring crack is always harder than a parallel one; a crack in a corner is easier than one on a flat face, because you can stem both walls; leaning cracks are the hardest. The video has embedding disabled, so watch it on YouTube.
Japanese climbing YouTuber TAKEMOVIE's beginner lesson starts on crack types at the 3-minute mark, then demonstrates hand jams, finger jams, thin hands, fists, offwidths and chimneys in turn. It works as a moving version of the whole map.
Something you can do tonight: measure your hand with a ruler: the widest part of your palm with fingers together, and the width across your knuckles when you make a fist. Save both on your phone. When you compare against cams later, you'll know whether your hand runs big or small.
The same crack is a different size for your hand
The table above has a trap: whose hand defines "hand size"?
Big and small hands each have their sizes
British crack climber Pete Whittaker (Wide Boyz) mapped, in his October 2026 newsletter, which cam sizes favour big hands and which favour small ones:
| Cam size | Big hands | Small hands | Who has it easier |
|---|---|---|---|
| 0.3, 0.4 | Little skin contact, a struggle | Fingers lock effortlessly | Small |
| 0.5 (purple) | Comfortable finger jams | Often forced into ring locks | Big |
| 0.75, 1 (green, red) | Forced into thin or paddle jams | Perfect hand jams | Small |
| 2 (gold) | A basic, solid hand jam | Often a cupped hand jam | Big |
| 4 (grey) | Fist jams | Butterfly stacks | Big |
| 5 | More solid stacks | Even stacks turn cupped and loose | Big |
| 6 | Forced toward the edges | More of the body fits inside | Small |
He illustrates it with a new route he and Mari Salvesen first-ascended in Kristiansund, Norway. The start is a hand crack: his big hands fit perfectly while Mari worked hard on cupped hands. The middle is a #6 offwidth roof, and there Mari cruised: her hips and shoulders went deeper, while he had to go inverted and do a massive sit-up. The finish is a #4 fist crack: he simply fist-jammed while Mari had to stack. Over the whole route, both felt it came out at the same grade.
Whittaker's conclusion: as long as you can get a fingertip in past the first joint, there's always a technique you can use; some are just easier and some harder. But for difficulty to even out, there's a catch: you have to climb every size. Stick to one size that happens to be bad for your hands and you'll decide you're not built for cracks.
It changes which routes you pick
That also explains why grades at Indian Creek in Utah confuse people. Julie Ellison writes in Climbing.com that many routes there were established by big-handed men, with hands around #2 and #3. So the typical hand crack goes at 5.10 while narrower cracks are usually 5.11, and for small-handed climbers those 5.11s climb easier than the 5.10s.
On Mountain Project, a woman whose hands are several sizes smaller than her husband's got the suggestion to look for climbs rated 5.11-, which would likely feel like 5.9 to her.
When it doesn't apply
The effect is clearest on splitters like Indian Creek's that stay one width end to end. On the UK's UKC forum, one climber said few British cracks are parallel enough for hand size to change the grade, though cruxes can still be easier or harder; others in the same thread named several UK routes that favour small hands.
Cam numbers are only where most people roughly land. One Mountain Project poster said that a #1 Friend (Wild Country's cam, sized differently from Camalots) is thumb stacks for him while a #0.5 Camalot is already ring locks, and asked people to "talk about techniques, not tools".
Something you can do tonight: next time you're at a gym crack wall, find the section where your jam feels best and ask a friend with cams to place one there. The size where the cam sits about half retracted is your "hand number". From then on, when a topo says "#1 hands", you'll know whether that means hand jams or thin hands for you.
The one thing every size shares
Whatever the width, the basic move is the same: insert in your thinnest shape, then expand or twist once it's in place, so bone holds you rather than muscle. The primer's five shared rules cover this in full, and every post after this one applies them.
In 2021 Wide Boyz made a fun video measuring how much pull each jam can hold on a force rig, from tips all the way to fists. It's an informal test by Pete and Tom Randall, so don't take the numbers too seriously. Watch the hand shapes instead: every size in one place, and how much the holding force changes when you switch jams at the same width.
Something you can do tonight: pause the video at each jam and match it to a size in the eight-size table at the top of this post.
Sizes pick crags, too
Each crag's rock and terrain make it known for certain kinds of crack. Before travelling to climb cracks, know what you'll meet:
| Crag | Rock | Known for |
|---|---|---|
| Indian Creek (Utah, USA) | Sandstone | Parallel splitters that stay one width, every size, where hand size shows most |
| Yosemite (California, USA) | Granite | Long routes, pin scars left by old pitons in finger cracks (see an ascent of Serenity Crack), offwidths |
| Joshua Tree (California, USA) | Granitic rock, rough surface | Flaring offwidths, often climbed with arm bars (VIDEORACLES' intro to offwidths) |
| Peak District gritstone (UK) | Coarse sandstone | Short, coarse cracks that test jamming, laybacking and friction (Climber.co.uk) |
| Ogawayama, Mizugakiyama (Nagano and Yamanashi, Japan) | Granite | Ogawayama is called Japan's Yosemite; Mizugakiyama's routes are bigger in scale (TOMMY CLIMBING CLUB) |
| Jogasaki (Shizuoka, Japan) | Andesite lava | Short sea-cliff cracks and roofs |
| Insubong, Seoninbong (near Seoul, South Korea) | Granite | Multi-pitch routes linking cracks and slab (Mountain Project), leaning cracks and chimneys |
| Long Dong (Taiwan) | Sandstone or metaconglomerate (sources differ), rough surface | Seaside trad; first routes like Noodle Line (5.8) at the First Cave are hand and fist cracks in a corner; tape up (see Taiwan's crags) |
Rough rock grips well but shreds your hands; smooth rock asks for more precise jams. Nobody has formally compared the same technique on both, so later posts only report what climbers say about specific crags.
Wide Boyz climbed a list of classic UK gritstone cracks called the "Cracker's Dozen", 13 routes from easy to hard, with Mari Salvesen along too. Green Crack, the fifth, starts at 2:13; Foord's Folly at 5:35 calls for thin hands; Ramshaw Crack at 10:17 widens from hands to fists to arm bars. It shows what short, coarse British gritstone cracks look like.
Something you can do tonight: open the Mountain Project or theCrag page for the next crag you want to visit, pick three classic cracks, and note which cam sizes they need. Compare those with your hand number to see which sizes you'll meet.
What to watch for in videos
Every post in this series embeds several videos. With crack videos it's easy to see only "they got up it". Three things are worth pausing for:
- Where the thumb and elbow point. Thumb up or down, elbow pulled down or flaring out, decides whether the jam holds.
- Where the feet are. Most of the work in crack climbing is in the feet. Watch whether they jam the foot in the crack, stand outside it, or bridge both sides.
- Same line, different people. Compare two or three people on the same route and differences in hand size and height jump out.
For example, Tom Randall of Wide Boyz climbs Indian Creek's Tricks Are For Kids (5.13) from 8:10 in Top 6 Super Splitters, and Brittany Goris has a video of the 70 m extension, which she grades 5.13c. Ogawayama's beginner classic Casablanca (5.10a) has been filmed by many climbers too, such as Japanese climber Chikugon in this ascent.
Edited ascent videos often cut the hardest move, and many Japanese and Korean videos have no subtitles, only a description of the moves. The description often lists the cam sizes used, which you can match against the size table above.
How to read the series
The series starts with hand cracks, the most secure and easiest to learn, and works outward toward narrower (fingers) and wider (fists, offwidths). Combination moves like laybacks, leaning cracks and roofs come once the single sizes are in place. Gear and training sit near the end as a toolbox, and the last post covers the crack crags of Japan and Korea:
| Order | Post | Question it answers |
|---|---|---|
| 0 | The crack size map (this post) | How wide is it, and which post do I read? |
| 1 | Hand cracks | How do I get a hand jam to hold my body weight? |
| 2 | Foot jams | How do I place my feet, how deep, and how do I make it hurt less? |
| 3 | Finger cracks | How do thumb-down finger locks and pin scars work? |
| 4 | Off-fingers and ring locks (in progress) | What do I do when fingers rattle and a hand won't fit? |
| 5 | Fist cracks (in progress) | How do I jam a fist so it doesn't rotate? |
| 6 | Offwidths (in progress) | When do I use arm bars, chicken wings and stacks? |
| 7 | Squeezes and chimneys (in progress) | Once I'm inside, how do I move up? |
| 8 | Laybacks, corners and leaning cracks (in progress) | When do I layback, and where do my hands go in a leaning crack? |
| 9 | Roof cracks (in progress) | How do I jam upside down and turn the lip? |
| 10 | Tape, gloves and crack shoes (in progress) | Tape or gloves, and which shoes? |
| 11 | Crack training and learning paths (in progress) | How can I train without cracks nearby? |
| 12 | Crack crags and videos of Japan and Korea (in progress) | Where should I go in Japan and Korea, and whose videos should I watch? |
At a minimum, read the hand and foot posts, then pick sizes based on the crag you're heading to. Placing protection isn't part of this series; for that, read the trad protection guide in the Sport and Trad Climbing series.
Practice questions: five scenarios
Answers are under each question. Think first, then open.
1. You put your fingers in a crack and they rattle, but your whole hand won't go in.
Answer
That's off-fingers, roughly cam sizes 0.5 to 0.75; read the off-fingers and ring locks post. If your hands are big, this width may be close to a finger jam for you; if they're small, you may need a ring lock.
2. A friend says a 5.10 hand crack at Indian Creek is "super easy". Your hands are much smaller than theirs.
Answer
Easy for them isn't easy for you. Many Indian Creek routes were put up by big-handed climbers, and the typical #2–#3 hand crack goes at 5.10. For small hands that width often means strenuous cupped hands, harder than a .75–#1 5.11. Ask which cam size it is and compare with your hand number.
3. You only climb one width on your gym's crack wall, keep struggling, and decide you're not built for cracks.
Answer
Whittaker says difficulty evens out, but only if you climb every size. That width may just be your hand's weak spot; at another size you might cruise past your friends. Find your hand number and start with the size that suits you.
4. A topo lists a "0.5 finger crack", and you're going with a friend who has huge hands.
Answer
By Whittaker's comparison, a 0.5 is a comfortable finger jam for big hands and often a ring lock for small ones. If your hands are smaller than your friend's, that section may call for off-finger technique, so read the off-fingers post and practise ring locks first.
5. You're watching a Japanese crack video with no subtitles and can only tell that "they got up".
Answer
Pause and check three things: which way the thumb and elbow point, whether the feet are in the crack or outside it, and whether someone else has filmed the same route for comparison. The description often lists the cam sizes and moves, which you can match against the size table above.
Next
Start with hand cracks. It's the size most people learn first and the most secure, and every other jam grows out of it.
References
- The crack-climbing primer
- A New FA in Kristiansund and the Golden Takeaway (Pete Whittaker, Wide Boyz newsletter, 2026)
- Wild Country Crack School Part 2 – Jamming (Tom Randall, UKC)
- The 10 Commandments of Indian Creek (Julie Ellison, Climbing.com)
- Resources for little hands and crack climbing? (Mountain Project forum, 2024)
- Crack climbs for small hands (UKC forum, 2021)
- When to switch from ring locks to tight hands (Mountain Project forum)
- Camalot C4 (Black Diamond)
- How to get good at crack climbing, lesson 1: basics (K Climbing Company, Kim Jong-sik, 2023, in Korean)
- Crack climbing basics, Part 1 (TAKEMOVIE, 2021, in Japanese)
- Which Crack Climbing Technique is Strongest? (Wide Boyz, 2021)
- How to be a Crack Master (Wide Boyz, 2022)
- Top 6 Super Splitters of Indian Creek (Wide Boyz, 2022)
- Tricks are for Kids Extension 5.13c (Brittany Goris, 2020)
- Ogawayama Casablanca 5.10a (Chikugon, 2023, in Japanese)
- How to Climb on Gritstone (Climber.co.uk)
- Crack Climbing: Intro To Offwidth Technique (VIDEORACLES, 2021)
- The FORBIDDEN 5.10 in Yosemite Valley – Serenity Crack 5.10d (The Gravity Lab, 2021)
- Crag guide (TOMMY CLIMBING CLUB, in Japanese)
- Insu-bong (Mountain Project)
- theCrag
- Ogawayama | Japan Climbing Crags
- Mizugakiyama | Japan Climbing Crags
- Jogasaki | Japan Climbing Crags
- Insubong | Korea Climbing Crags
- Seoninbong | Korea Climbing Crags
- Choosing a crag in Taiwan
- Trad protection: nuts, cams and the three conditions of a good placement
Update Log
- 2026-10-27: Foot jams and Finger cracks are published; the series table, the size table and the "at a minimum" line now link to them.