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Yarn Under vs Yarn Over in Amigurumi: The Real Cause of Stitch Slant—and How to Fix It with Twist, Tension, and Handedness

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CrochetWiz

February 6, 202617 min read
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Yarn Under vs Yarn Over in Amigurumi: The Real Cause of Stitch Slant—and How to Fix It with Twist, Tension, and Handedness

Why your amigurumi looks uneven: decode yarn twist (S vs Z), hook path, and left/right-hand bias. Learn practical fixes to match designer photos, prevent gaps, and standardize your patterns for consistent results.

Yarn Under vs Yarn Over in Amigurumi: The Real Cause of Stitch Slant—and How to Fix It with Twist, Tension, and Handedness

If your amigurumi faces, stripes, and seams don’t look like the designer’s photos—especially if the stitches seem to lean, textures look “X-like” instead of “V-like,” or gaps are showing where there shouldn’t be—there’s a high chance the culprit isn’t simply “tension.” It’s the interaction between your hook path (yarn over vs yarn under), the yarn’s twist (S vs Z), and your handedness. Once you see how these three dials work together, you can tune them and get predictable, photo-matching results.

This article is an opinionated, technical guide for amigurumi makers who want consistent, tight fabric, clean shaping, and stitch appearance that matches their patterns—without trial-and-error on every new project.

Executive summary (for the impatient)

  • The slant you see in single crochet in the round is a torque artifact caused by loop orientation and yarn twist interacting with how you form the stitch (YO vs YU) and whether you’re right- or left-handed. It is normal—but adjustable.
  • Yarn under (YU) often yields tighter, X-shaped stitches with fewer gaps, but it also changes stitch geometry and can exaggerate lean or bias depending on the yarn’s twist. Yarn over (YO) produces classic V-stitches and typically less slant in many yarn/tension combinations.
  • S vs Z twist matters. Using a technique that “untwists” your yarn for your handedness compromises stitch integrity and magnifies slant and splitting. Choose technique and yarn that add back or at least don’t remove twist as you crochet.
  • Three dials to fix the problem:
    1. Twist: match your technique to yarn twist (S or Z), or adjust how the yarn feeds to stop unplying.
    2. Tension: adjust hook size and loop control so the working loop isn’t distorting.
    3. Technique: standardize YO vs YU (and clearly label it) to match the designer’s photos.
  • To match designer photos quickly: identify if their sc looks V-like (likely YO) or X-like (often YU), note your handedness, check yarn twist direction, then swatch a 12–18-st spiral in both methods and pick the closest match.

References: Craft Yarn Council standards for baseline gauge practices; PlanetJune’s amigurumi help hub for amigurumi-specific technique clarity; general textile literature on S/Z twist and loop geometry [Craft Yarn Council, PlanetJune, Wikipedia Yarn].

Setting the vocabulary: YO, YU, S twist, Z twist, bias, and handedness

  • Yarn over (YO): The standard way to catch the yarn with the hook so the yarn travels over the hook’s spine. In single crochet, YO generally yields the familiar V-shaped top.
  • Yarn under (YU): Catching the yarn from underneath (the hook scoops the yarn), which flips the top legs of the stitch and tends to produce tighter, X-like stitches. Many amigurumists adopt YU to reduce gaps.
  • S twist vs Z twist: Direction of the yarn’s final visible twist. Look at the plies: if the diagonal on the yarn slopes like the center of the letter S (), it’s S-twist; if it slopes like Z (/), it’s Z-twist. Most mass-market, plied knitting yarns are commonly S-plied, but verify—many exceptions exist (especially in cottons, singles, and handspun).
  • Bias/lean: The directional slant of stitches or the spiral “drift” in amigurumi rounds. Single crochet in a continuous spiral naturally biases; technique and twist can amplify or reduce it.
  • Handedness: Right- vs left-handed crocheters mirror the hook path. That mirroring reverses how YO or YU adds or subtracts twist from the working yarn and how the loop is seated on the hook.

Why this matters: The same pattern, yarn, and hook can produce visibly different results across makers because each person’s twist–technique–handedness combo is unique. Understanding your combo lets you standardize your output.

References:

  • Craft Yarn Council (CYC) Standards and Guidelines: helpful for consistent gauge and terminology.
  • Wikipedia: Yarn—overview of twist and structure.
  • PlanetJune Amigurumi Help: practical, amigurumi-specific technique notes.

What actually causes stitch slant?

The short answer: torque. Each single crochet sets a loop on the hook, then draws a second loop through it. The way that loop is seated (front vs back leg dominance, twist of the crossing, and whether you YO or YU) preloads the fabric with torque. Worked in a spiral, those torques accumulate and present as a lean, a seam drift, or an apparent “spin” to the surface texture.

The longer answer involves three interactions:

  1. Loop orientation from YO vs YU
  • YO yields a standard mount: front leg of the top V sits slightly forward, back leg slightly back, with a familiar V facing you.
  • YU reverses the loop’s crossing angle so the legs pinch into an X at the top. This tightens the stitch and reduces visible holes, but also changes how the loop resists lateral forces, often increasing apparent lean on some yarns.
  1. Yarn twist and twist exchange
  • Your hook path either adds twist to the working yarn or removes it. When your technique removes twist from an S-plied yarn as you work, the yarn becomes more open, more split-prone, and less resilient, and the stitch’s resistance asymmetry increases—amplifying slant. If you instead add a small amount of twist back (or at least don’t remove it), the stitch stands up straighter.
  1. Handedness and direction of work
  • Right-handed vs left-handed paths mirror the above effects. A YO that stabilizes twist for a right-handed crocheter may remove twist for a left-handed crocheter, depending on feed and how the ball is oriented. The same is true for YU.

There is no universal “best” between YO and YU for amigurumi. There is only the best choice for your twist–technique–handedness combo and for the visual result you want.

References:

  • Wikipedia: Yarn (twist direction basics)
  • Craft Yarn Council: Standards (for consistent expectations around hook sizes and gauge)

Diagnose your combo with two 10-minute swatches

You can isolate your variables and pick a winning combo today. Use your target yarn and hook.

Swatch A: Spiral single crochet (no turning)

  • Make a 16–24 stitch magic ring.
  • R1: 6 sc. Work continuous rounds, increasing by 6 evenly per round to reach ~36 stitches over 5 rounds.
  • Work one more plain round (no increases), then fasten off.
  • Observe: Do stitches look like Vs or Xs? Is slant obvious? Is the fabric tight enough for stuffing?

Swatch B: Turned single crochet (turn at end of each round)

  • Repeat the above swatch, but slip stitch to join at the end of each round and turn your work. Alternate right- and wrong-side rounds.
  • Observe: Turning cancels bias. Note if this fixes the lean even with the same technique.

Repeat both swatches for YO and YU. If you’re left-handed, do the same. Compare four discs:

  • Which disc matches the designer’s photo texture (V vs X)?
  • Which disc shows the least slant?
  • Which disc feels least splitty while working?

Keep the winner as your default for that yarn class.

Reference: PlanetJune’s troubleshooting of spiral vs turned rounds is a practical guide for amigurumi makers [PlanetJune].

How to read yarn twist quickly (and why it matters)

  • Visual test: Hold the yarn taut. Look at the diagonal of the plies.
    • S-twist: Diagonals slope like \\ (same direction as the central stroke of the letter S).
    • Z-twist: Diagonals slope like /// (same direction as the central stroke of the letter Z).
  • Drop test: Cut a 30–50 cm length and let it hang. If it kinks clockwise when relaxed, it’s loaded with Z bias; counterclockwise suggests S bias. This is rough, but useful if visual plies are fuzzy.
  • Label reality check: Most mainstream multi-ply knitting yarns are S-plied. Many singles (unplied) are Z-twisted. Handspun and some cottons vary widely. Always check.

Why it matters:

  • Right-handed + YU + S-plied yarn often removes twist from the working yarn (you’ll see the plies open). This produces very tight stitches with an X look but risks splitting and exaggerated lean.
  • Right-handed + YO + S-plied yarn tends to preserve or add back a touch of twist, stabilizing the stitch, reducing splitting, and yielding clean Vs.
  • Mirror these heuristics for left-handed crocheters: left-handed YO can behave more like right-handed YU with respect to twist exchange, and vice versa. Test; don’t guess.

Reference: General textile sources on S/Z twist and crochet loop geometry; see Wikipedia’s Yarn entry and spinning literature (Spin Off Magazine, general references) for fundamentals.

Hook path and handedness: what your hook is actually doing

Consider how the hook catches yarn:

  • YO path: The yarn travels over the hook’s throat. From the maker’s viewpoint, the yarn wraps in a direction that usually adds a fraction of twist back into S-plied yarn for right-handers.
  • YU path: The hook scoops the yarn from under. For many right-handers with S-plied yarn, the working wrap slightly untwists as it’s drawn through. The visual result is a tighter, X-like top with stronger lateral grip.

Because left-handed crocheting mirrors this geometry, the net twist exchange swaps roles. That’s why some left-handed makers get straighter fabric with YU and others with YO—exactly the opposite of their right-handed peers using the same yarn.

Practical note: Hook shape influences this too. Inline hooks (e.g., Bates-style) vs tapered hooks (e.g., Boye-style) change how the yarn slides and whether it splits under YU. If your YU samples are splitting, try a different hook profile before abandoning the technique.

The three dials you can turn: twist, tension, technique

You can treat bias as a controllable outcome.

  1. Twist dial
  • Choose yarn twist that suits your technique and handedness. If your preferred technique removes twist (opening the plies), pick a yarn whose twist direction offsets that effect (e.g., try Z-twist or more tightly S-plied yarns).
  • Control feed direction. Pulling from the center-pull cake vs from the outside can subtly add or remove twist to the working yarn as you crochet. If your yarn is unplying under your hands, try flipping the cake or pulling from the other end.
  • Add back twist occasionally. For long sessions where you notice the yarn flattening, let the hook dangle and spin to re-twist the working yarn, or manually roll the ball to restore twist.
  1. Tension dial
  • Reduce working-loop distortion. The single biggest tension win in amigurumi is easing up on the height of the working loop before completing the stitch. Keep the loop snug but not choked.
  • Adjust hook size. If switching YO to YU to reduce gaps feels too tight, go up one hook size; if sticking with YO leaves gaps, go down one.
  • Control draw-through speed. A smooth, single-motion draw-through reduces partial de-twisting compared to a stop-start motion that lets the yarn unwrap on the hook.
  1. Technique dial
  • Standardize and explicitly choose YO or YU for amigurumi. YO gives classic V-stitches; YU gives a tighter X fabric. Pick one per project and state it.
  • Turn some rounds. If you love the YU texture but see too much lean in spirals, work joined, turned rounds to cancel bias. This is common in colorwork spheres to keep features aligned.
  • Switch decreases. Invisible decreases (worked under the front loops of the next two stitches) minimize holes regardless of YO/YU and reduce bias at shaping points.

Matching designer photos: a practical protocol

If a pattern doesn’t specify YO or YU (many don’t), and you want your result to match photos closely, use this checklist.

  1. Identify the stitch look in the photos
  • V-like tops and a more “knit-like” surface suggest YO.
  • X-like tops with a crisscross texture suggest YU.
  • Note gaps: if the fabric looks very dense and smooth with minimal air holes, they may be using YU, a smaller hook, or both.
  1. Detect handedness clues
  • Seam placement in the sample: If the seam drifts in a particular direction, it may reveal the designer’s handedness when combined with whether they work continuous spirals. Some designers note this explicitly.
  • Mirror imaging: If photo tutorials show the hook in the left hand, mirror your expectations.
  1. Consider the yarn brand and fiber
  • Cotton splits and opens more if twist is removed; acrylics are more forgiving. Many mainstream acrylics are S-plied; some mercerized cottons are tightly Z-twisted singles or balanced plies. If the brand is listed, look closely at its ply direction.
  1. Swatch audit
  • Make two quick discs (YO and YU) as described earlier. Match the texture first, then evaluate bias. If bias is excessive, test turned rounds.
  1. Lock your choice
  • Once matched, standardize your technique for the rest of the project. Mark your pattern notes: “This pattern: YO, turned rounds on colorwork; HOOK 2.5 mm; S-plied yarn.”

References:

  • Craft Yarn Council: good baseline for hook/yarn sizing.
  • PlanetJune: abundant amigurumi-specific finishing and shaping guidance that reflects real-world photo results.

Preventing gaps without wrecking geometry

YU is popular in amigurumi because it often eliminates gaps. But you don’t have to accept exaggerated bias or splitting as the price.

Options to reduce gaps while preserving stability:

  • Keep YO and go down a hook size. This often seals holes and keeps V-stitch geometry (matching many designer photos).
  • Use a denser yarn. High-plies or slightly heavier category yarns fill space better without choking the stitch.
  • Use invisible decreases and thoughtful increases. Holes often appear at shaping points; technique changes can solve those without switching the whole stitch formation.
  • Turn rounds strategically. If you love the YU look but the spiral drift ruins a face, convert to joined, turned rounds for those sections.
  • Slightly roll the ball as you work (or flip the cake) to keep the yarn from unplying if your technique tends to remove twist.

Special cases: stripes, faces, and surface alignment

  • Horizontal stripes: Spiral rounds produce a stairstep in color changes and emphasize bias. Use jogless joins with turned rounds to keep stripes level.
  • Faces and feature alignment: Bias can “walk” safety eyes and embroidered mouths off-center as the head grows. Turned rounds or pre-planning the drift can compensate.
  • Dense stuffing: Overstuffing magnifies any visible slant because stitches are forced apart. Stuff firmly but incrementally; support the fabric from the inside with a palm while shaping to avoid stretching only one direction.

Pattern standardization: how designers can help (and how makers can self-document)

For designers:

  • Declare your stitch formation. Add “All single crochet are worked with YO (standard) unless noted” or “This pattern uses YU for a tighter fabric.”
  • Specify rounds method: “Work in continuous spirals” vs “Join and turn each round.”
  • List yarn twist and key properties: “Sample shown in [Brand, color], S-plied.” If unsure, add a photo-inset of the yarn close-up.
  • Provide a gauge swatch photo of 20–25 sc in the round showing the texture clearly. This lets makers visually match technique even if their per-inch gauge differs.
  • Handedness note: “Photos show right-handed demonstration; left-handed makers mirror images.”

For makers:

  • Add technique to your project notes: YO or YU, turned or spiral, hook size, yarn twist.
  • Keep a personal reference sheet with four discs (YO/YU × spiral/turned) in your favorite yarn category and hook size. Use it to decide quickly on new patterns.

Reference: Craft Yarn Council for how to write gauge and materials consistently; PlanetJune for amigurumi pattern-writing best practices.

Myth-busting

  • “YU is better for amigurumi.” It’s better at reducing gaps for many yarns, yes—but only if it doesn’t wreck your yarn’s twist or create bias you don’t want. Choose by fabric outcome, not dogma.

  • “My amigurumi leans because I’m doing something wrong.” Spiral bias is normal. You can minimize it by turning rounds, by adjusting technique, or by selecting yarn whose twist complements your path.

  • “Left-handers must always mirror patterns.” Not always. Most amigurumi shaping is symmetric. What matters more is recognizing that left-handed technique may interact differently with yarn twist; pick the combo that yields the visual match you want.

  • “Blocking will fix lean.” In stuffed 3D crochet, blocking does little. Control bias in the construction stage instead.

Recipes: quick fixes by symptom

Symptom: Fabric is gappy; stitches look like Vs; bias acceptable.

  • Fix: Keep YO; go down 0.5–1.0 mm hook; tighten working loop slightly; use invisible decreases.

Symptom: Fabric is tight and gap-free; stitches look like Xs; noticeable bias; yarn splits.

  • Fix: Try YO with the same hook; or flip cake/pull from the other end to avoid unplying; or switch to a more tightly plied yarn; or work joined, turned rounds.

Symptom: Head shape drifts; safety eyes won’t sit symmetrical.

  • Fix: Turn rounds for the midsection of the sphere; mark the front every round; adjust increases to counter drift or switch technique temporarily.

Symptom: Cotton opens and splits with YU.

  • Fix: Use YO; switch to an inline hook; or choose a mercerized, tightly spun cotton; or slightly increase hook size.

Symptom: Z-twist single behaves oddly (twangy, over-twisted loops) with YO.

  • Fix: Test YU; or feed yarn from the direction that neutralizes over-twist; slow down draw-through to avoid adding extra twist.

A closer technical note: why X vs V stitches behave differently

In single crochet, the orientation of the top legs determines how the load from the next stitch is distributed:

  • V topology (YO): the legs open toward you, and the next stitch’s entry tends to seat the loop symmetrically over the post. The fabric can flex without a preferred lateral direction.
  • X topology (YU): the crossing constrains lateral flex more on one diagonal than the other, which resists opening (good for no gaps) but can favor a slight rotational torque. When compounded in the round, you see more pronounced spiral lean in some yarn/handedness combinations.

This is also why YU fabrics can appear smoother in amigurumi spheres (fewer holes) but occasionally look more “twisted” overall. The net effect is neither good nor bad—it’s a design choice.

Building a repeatable workflow for consistent results

  • Step 1: Identify the visual you want (match the designer’s photos: V vs X texture).
  • Step 2: Check your yarn twist (S or Z). Record it.
  • Step 3: Make two fast discs (YO and YU) in your yarn. Pick the match.
  • Step 4: If bias remains an issue, decide: turned rounds, or change technique/yarn feed.
  • Step 5: Lock in the combo for the whole project and note it at the top of your pattern.

This eliminates guesswork from project to project. Over time, you’ll learn which yarns and techniques are your defaults.

References and further reading

Note: Exact interactions between technique, twist, and handedness vary with specific yarns, hook shapes, and personal motion. The tests in this article are designed to give you repeatable, yarn-specific answers rather than one-size-fits-all rules.

Final takeaway

The “real cause” of slant in amigurumi isn’t just your stitch choice in isolation. It’s the dynamic trio—yarn twist, hook path, and handedness—creating a bias that you can see and control. Once you treat these as dials you can tune, you’ll consistently produce the fabric you intended: smooth, tight, aligned, and photo-accurate to the pattern you’re following. And you’ll have a reliable checklist to match any designer’s texture on the first try.