White & Blue Jellyfish Keychain Crochet - The Dome Geometry

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White & Blue Jellyfish Keychain Crochet - The Dome Geometry

★★★★★ 4.7 · 12

Dana Whitlock16.07.2026JUMP TO TUTORIAL

I came to this little project the way I come to every amigurumi shape — by asking what the geometry actually is before I pick up a hook. A jellyfish keychain is really just a dome (not a full sphere, thank goodness, that's a different increase schedule entirely) with a fringe of tentacles hung off its equator. Seven stages, one skein of white and a whisper of blue, and I'll show you the math at every turn so your dome comes out round instead of lopsided.

Reading the Materials Before You Ever Touch the Hook

I lay everything out before I start, the way Aunt Carol never did and I always do — old habits from eleven years of grading papers, I suppose. In this flat lay you can see the whole material budget for one jellyfish: a full skein of white cotton for the dome, a much smaller wind of light blue cotton for the tentacles, a steel hook, safety eyes, stuffing, and the keyring hardware that turns a toy into a charm.

• Yarn weight matters more than yarn color here. A DK-weight cotton with a snug hook gives you fabric tight enough to hold stuffing without gapping — the whole reason amigurumi uses a smaller hook than the yarn label recommends.
• Cotton over acrylic holds its shape under the tug of a keyring clasp, which acrylic's stretchier fiber will eventually surrender to.
• Buy the blue skein small on purpose — tentacles use surprisingly little yardage, and I'd rather you have leftover blue for a second jellyfish than a second skein gathering dust.

Starting the Dome: Why a Magic Ring, Why Six

In this second photo I've just begun the increase rounds that build the rounded top of the head, and this is where the geometry actually lives. A flat circle increases by six stitches every round to stay flat — that's the constant your amigurumi teachers all quoted without explaining. But a dome isn't a flat circle: it's a circle that stops increasing partway through and goes vertical instead, which is exactly what turns a disc into a bell shape.

My rule of thumb, worked out with a tape measure and more patience than I'd like to admit: increase every round until your piece measures roughly two-thirds of your target head diameter, then switch to straight rounds. For a 5 cm (2 in) tall jellyfish head, that's about four increase rounds before you go flat.

The increases are the curve. The straight rounds are the wall. Confuse the two and you get a flying saucer instead of a jellyfish.

The Straight Rounds — and Stuffing Early, Not Late

By this photo the dome is roughly half-built, and you can already see fiberfill peeking out from the bottom — I stuff as I go, not at the end, and I'll die on this hill. Stuffing after the fact means fighting the opening with your fingers and a stitch marker; stuffing in stages means every round closes around fluff that's already settled where it belongs.

• Add stuffing in three passes, roughly every four rounds, rather than one big handful at the end.
• Pinch, don't cram. Overstuffing stretches your stitch definition and the dome loses that crisp, rounded profile you can see forming here.
• Straight rounds should equal your increase-round stitch count exactly — if you're drifting up or down a stitch, count back to your last increase round before you go further.

This is also the stage where I check my work against gauge, the same way I'd check a swatch for a sweater. If your dome is ballooning wider than expected, your tension has loosened; drop a hook size before you stuff another round.

Closing the Dome and Placing the Eyes by Formula, Not by Eye

The eye-spacing formula I actually use

Once the dome is fully stuffed and closed at the bottom — which you can see happening here, safety eyes going in before the last few stitches are permanently sewn shut — the temptation is to just eyeball the placement. I never do, and I'd rather teach you the two-second math instead of the hope.

Take your dome's stitch count around the widest round (call it N). Divide N by 4: that gives you the horizontal gap, in stitches, between where each eye sits from the center front. For a 24-stitch round, that's 6 stitches out from center on each side — symmetric, no guessing, no crossed-eyed jellyfish staring back at you from the sunroom shelf.

Insert eyes before final stuffing is complete, while you can still reach a finger inside to secure the safety washer. Trying to attach eyes after the opening is fully closed is a lesson I only had to learn once.

Tentacles Are Just Long, Skinny Chains — Here's the Count

This is my favorite photo of the set, honestly — the finished white head sitting there with its two calm black eyes while a fistful of loose blue chains pool on the table, waiting. Tentacles are the least mathematically fussy part of this whole build: they're simple chains, single-crocheted back along themselves for texture, no shaping required.

1. Chain 18–22 stitches per tentacle for a keychain-scaled jellyfish — longer if you want a dramatic trailing effect, shorter for something that survives a backpack zipper better.
2. Single crochet back down the chain for a firmer, slightly ribbed tentacle that holds its curl.
3. Make 8 to 10 tentacles — I land on 9 for this size, which divides reasonably evenly around a 24-stitch base circumference without me doing long division mid-project.

Vary two or three lengths slightly. Real jellyfish tentacles are never uniform, and neither is the charm of a handmade one.

Sewing the Tentacles: Even Spacing Around the Circumference

Here I'm halfway through attaching tentacles to the bottom edge of the head, half secured and half still dangling — and this is the moment where careless spacing shows up worst, because uneven tentacles read instantly as “off” even to someone who's never touched a hook.

The fix is the same division I used for the eyes: take your bottom-round stitch count and divide by your tentacle count. Nine tentacles around a 24-stitch round doesn't divide cleanly, and that's fine — alternate gaps of 2 and 3 stitches rather than forcing an uneven single gap somewhere that your eye will find every time. Sew each tentacle on with a few firm whip stitches through the base of the strand, not just a surface tack, since this is the point that takes all the stress when the keychain gets tugged out of a bag pocket.

The keyring sits ready in this shot, waiting for its turn once the last strand is on.

The Finished Jellyfish — and Why the Math Was Worth It

And here's the payoff: a rounded white dome with its calm black eyes, nine pale blue tentacles trailing beneath it, keyring clipped neatly at the crown. Attach the split ring through a few stitches at the top-center of the head — centered, using the same halving logic from the eye placement — so the finished piece hangs straight rather than listing to one side on your keys.

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What strikes me every time I finish one of these isn't the cuteness, though I'll admit it's considerable. It's that every proportion you see — the dome's roundness, the eyes' symmetry, the tentacles' even fan — came from four or five simple divisions, not from luck or a steady hand. That's the whole argument of this blog in miniature.

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White & Blue Jellyfish Keychain Crochet - The Dome Geometry

★★★★★ 4.7 · 12 ratings

Learn my crochet flower blanket pattern with graded granny squares, gauge math, and a scalloped border, built stitch by stitch with photos and no guesswork.

Amigurumi Keychainwhite blue jellyfish keychain crochet

PREP TIME10 min

Work Time90 min

TOTAL TIME100 min

Yield1 jellyfish keychain

DifficultyMedium

Costapprox. $8

Materials

• Materials
• 1 skein white DK-weight cotton yarn (approx. 50 g)
• 1 small skein light blue DK-weight cotton yarn (approx. 20 g)
• 1 steel crochet hook, 2.5 mm
• 1 pair black safety eyes, 6 mm
• 1 keyring with lobster clasp, 25 mm split ring
• Polyester fiberfill stuffing, small handful
• Yarn needle for weaving in ends and sewing tentacles
• Small sharp scissors
• 1 stitch marker

Steps

1

Set up your gauge swatch

Work a small circle in white cotton with your 2.5 mm hook and check that your stitches sit tight enough to hold stuffing without gaps; drop a hook size if the fabric looks loose.

2

Start the dome with a magic ring

Work 6 single crochet into a magic ring, then increase by 6 stitches every round for approximately four rounds, until the piece measures about two-thirds of your target head diameter.

3

Work straight rounds

Switch to single crochet without further increases, working straight rounds until the dome reaches your desired height, adding fiberfill in three separate passes as you go.

4

Attach the eyes and close the base

Insert safety eyes symmetrically, spaced at one-quarter of your round's stitch count out from center front on each side, then finish stuffing and close the remaining stitches with a needle.

5

Chain the tentacles

Chain 18 to 22 stitches in light blue, then single crochet back down each chain; repeat to make 8 to 10 tentacles of slightly varied length.

6

Sew tentacles to the base

Divide the bottom round's stitch count by your tentacle count to find even spacing, then whip stitch each tentacle firmly through the base of the strand around the edge.

7

Attach the keyring

Sew the split ring through a few stitches at the top center of the head so the finished jellyfish hangs straight, then weave in all remaining ends.

Hi! I'm Dana

Hi, I'm Dana! Math teacher for 11 years, crocheter for 27, and the numbers nerd behind Yarn Wren. I design crochet garments genuinely graded…

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Wrapping Up

This is a small project, barely an afternoon's work with tea nearby, but it holds the same bones as everything I teach on this blog — shape comes from numbers you can name, not from hoping your hands know best. Clip yours onto a bag, give it to someone who likes odd little sea creatures, and keep the leftover blue for a second one. May your gauge be true, Dana