How to join granny squares: joins and yarn compared

The main joins at a glance

Every join is either worked with a tapestry needle, worked with a hook after the squares are finished, or worked with a hook during the last round of each square. The table sets out what each one looks like, how much give it has and how much yarn it takes, using the designers’ own descriptions. Where a cell says no figure found, we couldn’t find a designer who states one.

For the stitches themselves, follow the designers’ tutorials listed at the bottom of this page. Simply Yarn and B.Hooked each walk through five or six joins with photos, Look At What I Made covers the zipper join, Sunflower Cottage Crochet the flat braid, and B.Hooked’s classic granny blanket and Make & Do Crew’s Dahlia blanket show join-as-you-go step by step.

Flat or ridged: what you’ll see

The flattest joins pick up only one loop of each edge stitch. Dedri Uys of Look At What I Made describes her zipper join as a flat cable on the front and a running stitch on the back, and Simply Yarn says it lies almost completely flat without ruffling the squares. B.Hooked calls the invisible seam, worked with a needle through the back loops, completely flat. Jera’s Jamboree joins Blossom Cottage with mattress stitch for an almost invisible seam.

Crocheted seams stand up more. The Patchwork Heart’s double crochet join, worked from the front, forms a ridge on top of the blanket, and B.Hooked notes that a single crochet join won’t lie completely flat. Marching North wants a ridge: the zigzag slip stitch join in her Sea Glass & Sand blanket leaves a visible one that gives a quilted look. If you want the ridge to show, use a contrast colour. If you want it to disappear, use the colour of the squares’ last round.

Stretch and strength

Simply Yarn finds whip stitch solid, which suits sturdy things, but says it isn’t great where you need some stretch, such as a garment. Its needle-weave join has more give. B.Hooked suggests the invisible seam for flexibility and softness in a blanket.

Slip stitch joins depend on your hand. Dedri Uys warns that slip stitches aren’t as elastic as other stitches, so work them loosely or the seam won’t give. At the other end, Sunflower Cottage Crochet says the flat braid join has a lot of movement and lets a blanket drape. The Patchwork Heart calls its double crochet join very strong.

How much yarn a seam takes

Designers rarely give the joining yarn on its own, and we found only two figures we could turn into a ratio. LoveCrafts tells you to cut about three times the seam length for mattress stitch; its tutorial is written for knitting, but the seam is sewn the same way. Dedri Uys leaves a 1m tail on each square and uses it to zipper-join her 10cm Iced Pie squares as she goes. An 8 × 8 Iced Pie layout has 112 edges to join, 11.2m of seam, against 64m of tails, so that’s at most 5.7 times. Purl Soho threads about a yard (91cm) at a time for whip stitch, but doesn’t say how many edges one length covers, so we haven’t turned it into a ratio.

That gives roughly 3 to 6 metres of yarn per metre of seam, including tails. It rests on those two figures only, so treat it as a starting point. These are the designers’ figures; we haven’t joined these blankets ourselves. We found no published figure for a double crochet seam or a flat braid. Both add chains or taller stitches, so plan for the top of the range or above until you’ve measured a test seam.

Count the seams in your grid

A grid of squares across × squares down has this many square edges to join: down × (across − 1) + across × (down − 1). Multiply by the side of one square to get the seam length. Worked as long seams instead, that’s (down − 1) seams running across and (across − 1) running down. Marching North’s 9 × 11 throw has 10 horizontal and 8 vertical seams, which fits.

The table below uses grids from our guide How many granny squares do I need for a blanket?, including Attic24’s 9 × 14 Harmony. Joining yarn is the seam length times 3 to 6. It doesn’t include the border. As a guide to weight, 100m of Stylecraft Special DK is about 34g.

Join-as-you-go uses no seam yarn, but a bigger last round

With join-as-you-go, the last round of each square doubles as the seam, so there’s no separate joining yarn. Instead, the colour of that last round needs more balls than you might expect. Haak Maar Raak’s Rainbow Granny Square Blanket asks for 6 balls of its joining colour for the last round of 135 squares and a 4-round border, about 13m per square. Simply Yarn’s granny baby blanket uses about 650m of cream for the joining round of 100 small squares and a 4-round border, about 6.5m per square.

Several patterns buy one colour for the outer round, the joins and part of the border, so you can’t separate the join. Marching North’s Sea Glass & Sand is like that: 6 skeins of Light Taupe cover round 5 of 84 squares, 15 whole squares, every join and two border rounds. In the granny-square designer, enter that shared colour’s join and border as one figure.

Measure a test seam before you buy

Cut 2m of your joining yarn, join two of your own squares with the method you’ve chosen, and measure what’s left. The difference is the yarn for one edge, tails included. Multiply it by the number of edges in your grid and you have a joining figure you can trust more than any of the ratios above.

Put that figure into the joining and border box of the granny-square designer, together with your border, and it works out the balls of each colour. For the 6 × 8 grid of 12cm squares in our guide to yarn per granny square, the join alone comes to 30 to 59m on these figures, before any border.

Common questions

Sources and scope

• simply-yarn.com/guides/how-to-crochet/how-to-join-crochet-shapes-together
• bhookedcrochet.com/2023/07/28/how-to-join-granny-squares-5-simple-ways/
• lookatwhatimade.net/crafts/yarn/crochet/join-crochet-squares-completely-flat-zipper-method/
• lookatwhatimade.net/crafts/yarn/crochet/free-crochet-patterns/iced-pie-square-crochet-pattern/
• www.purlsoho.com/create/sewing-crocheted-squares-together/
• www.lovecrafts.com/en-us/blogs/articles-us/how-to-mattress-stitch
• www.thepatchworkheart.co.uk/2015/05/joining-squares-method-1-crochet.html
• sunflowercottagecrochet.com/how-to-crochet-the-flat-braid-join/
• www.marchingnorth.com/crochet-granny-square-blanket-free-pattern/
• makeanddocrew.com/dahlia-crochet-granny-square-blanket-part-3/
• attic24.co.uk/posts/harmony-blanket/
• haakmaarraak.nl/free-crochet-pattern-colourful-rainbow-granny-square-blanket
• simply-yarn.com/crochet-patterns/easy-free-granny-square-baby-blanket-crochet-pattern
• www.jerasjamboree.co.uk/granny-square-blanket-blanket-blossom-cottage/
• sarahmaker.com/granny-square-blanket/
• www.anniedesigncrochet.com/scrap-buster-cal-free-granny-crochet-blanket-pattern/
• www.anniedesigncrochet.com/floral-granny-square-blanket-free-crochet-pattern/
• www.stitchandstory.com/blogs/our-journal/chunky-granny-square-blanket
• bhookedcrochet.com/2024/10/08/how-to-make-a-classic-granny-square-blanket-in-3-sizes/
• www.stylecraft-yarns.co.uk/yarns/special-dk

Sources checked 2 October 2026. Label facts come from the linked references; worked purchase examples and arithmetic are our own illustrations.