Round Crochet Coaster with a Scalloped Shell Edge

A shell edge is one of the quickest ways to dress up a plain circle: one extra round turns a flat double crochet disc into a coaster with twelve even scallops. The only real requirement is arithmetic. The shell repeat in this pattern uses four stitches, so the last round of the circle has to be a multiple of four. A standard double crochet circle gives you 48 stitches after four rounds, which divides into exactly twelve shells with nothing left over.

This pattern uses US crochet terms throughout.

What You Need

• Worsted weight (#4) cotton yarn in one color, or two if you want a contrast edge
• US H-8 (5 mm) crochet hook, or US G-6 (4 mm) for a denser fabric
• Yarn needle and scissors

Worked as written, the coaster comes out at about 5 in (13 cm) across from scallop to scallop. That is an estimate: gauge varies from one crocheter to the next, and a smaller hook or thinner yarn will shrink it. If you would rather have a smaller coaster, there is a three-round version further down. For help choosing a target, see the coaster size guide.

Abbreviations and Notes

• ch — chain
• sl st — slip stitch
• sc — single crochet
• dc — double crochet
• st(s) — stitch(es)
• shell — 5 dc worked into the same stitch

The circle is worked in joined rounds, not a spiral. Every round begins with a chain 3 that counts as the first double crochet, and ends with a slip stitch into the top of that chain 3. Do not turn the work between rounds.

Crochet the Circle

The first four rounds are the same construction as the classic round double crochet coaster: twelve stitches in the ring, then twelve more in every round.

1. Rnd 1: Make a magic ring. Ch 3 (counts as dc), work 11 dc into the ring, pull the tail to close the ring, sl st to the top of the ch 3. (12 dc)
2. Rnd 2: Ch 3 (counts as dc), dc in the same st, 2 dc in each of the next 11 sts, sl st to the top of the ch 3. (24 dc)
3. Rnd 3: Ch 3 (counts as dc), dc in the same st, dc in the next st, *2 dc in the next st, dc in the next st; repeat from * 10 more times, sl st to the top of the ch 3. (36 dc)
4. Rnd 4: Ch 3 (counts as dc), dc in the same st, dc in each of the next 2 sts, *2 dc in the next st, dc in each of the next 2 sts; repeat from * 10 more times, sl st to the top of the ch 3. (48 dc)

Count before you go on. The shell round only closes neatly on exactly 48 stitches, and it is far easier to fix a missed increase now than to discover half a shell at the end.

Work the Shell Round

Each repeat covers four stitches of round 4: one stitch takes a single crochet, the next is skipped, the next takes the whole shell, and the last is skipped. The single crochets pin the edge down and the five double crochets fan out between them.

5. Rnd 5: Ch 1 (does not count as a st), sc in the same st as the join, *skip 1 st, 5 dc in the next st, skip 1 st, sc in the next st; repeat from * 10 more times, skip 1 st, 5 dc in the next st, skip 1 st, sl st to the first sc. (12 shells, 12 sc)

That is 60 double crochets and 12 single crochets, 72 stitches in all, sitting on the 48 stitches below. Fasten off and weave in the ends.

Why the Count Has to Be a Multiple of Four

Add up one repeat: single crochet (1), skip (1), shell (1), skip (1). Four stitches are used every time, so the round you are working into must divide evenly by four. Here is how the standard double crochet circle lines up:

For a smaller coaster, stop after round 3 and work the shell round over 36 stitches. Follow round 5 as written but repeat the starred section 7 more times instead of 10, then finish with the final shell. You will have 9 shells and 9 single crochets, and a coaster of roughly 4 in (10 cm).

If you adapt a different circle and its count does not divide by four, add or remove increases in the last plain round until it does. The same shell repeat appears among the borders in the guide to crochet coaster edging, where it is worked on straight edges too.

Adding the Edge in a Contrast Color

A second color makes the scallops stand out, as in a cream circle with a honey edge. Work rounds 1 to 4 in the main color and fasten off. Then:

1. Join the contrast color with a sl st in any stitch of round 4.
2. Ch 1, sc in that same stitch.
3. Continue round 5 from the first asterisk exactly as written.

You can start in any stitch; the count is the same from every starting point.

Keeping the Scallops Flat

A shell edge adds stitches quickly, and on a circle that is usually what the outer round needs. Two things can still go wrong:

• The scallops curl upward. The shells are tight. Loosen the double crochets a little, or pull each one up slightly taller before finishing it.
• The edge ripples. The shells are loose or the circle underneath has too many stitches. Recount round 4 first, then try a hook one size smaller for round 5 only.

If the circle itself is cupping or waving before you reach the edge, the shell round will not correct it. Sort that out first with the advice in how to keep crochet coasters flat.

Blocking and Finishing

Scallops benefit from blocking more than most edges. Dampen the coaster, lay it on a blocking mat or folded towel, and put one pin through the middle of each shell so the twelve points sit evenly spaced. Leave it until it is completely dry. Follow the yarn label for washing and for whether the fiber tolerates steam.

Weave each tail through the back of several stitches in more than one direction before trimming, so the ends do not work loose in the wash. On a two-color coaster, weave each tail into stitches of its own color so it stays out of sight.