Finishing
Joining Granny Squares: 4 Methods Compared
Four joins cover nearly every granny square project: whip stitch through back loops (fastest needle join, flat, faint ridge on the front), mattress stitch (invisible from the front, slowest), slip stitch (quick and sturdy, leaves a firm ridge best used as a design feature), and join-as-you-go (no seaming session at all, but committed square by square). On a 48-square throw the yardage cost runs from about 30 yards for whip stitch to 55 for slip stitch. Whichever you choose, block the squares first — joins amplify size differences, never hide them.
Forty-eight finished squares is not a blanket; it is a decision point. The join decides how the blanket looks, drapes, and survives the wash — and every method’s advocates present theirs as the obvious one. Here are the four that matter, with what each actually costs.
The comparison
| Method | Front appearance | Speed | Seam bulk | Yarn per seam edge* |
|---|---|---|---|---|
| Whip stitch (back loops) | flat, faint dashes | fast | low | ~0.65 yd |
| Mattress stitch | invisible | slow | none | ~0.75 yd |
| Slip stitch | firm ridge | fast | high | ~1.1 yd |
| Join-as-you-go | integrated, lacy | no seaming session | low | ~0.9 yd |
*4.5-inch square edge, worsted weight, measured by weighing seam samples.
Whip stitch: the honest default
Squares right sides together, yarn needle, and a whip stitch through the back loops only of each pair of stitches — through-both-loops works but doubles the ridge. Back loops leave the front loops kissing at the surface, which is why the seam reads as a neat dashed line rather than a welt. It is the fastest needle join, tolerates minor size mismatches, and is the right answer for a first blanket.
Mattress stitch: invisible, and priced accordingly
Both squares face up, edge to edge; the needle picks up the bars just inside each edge, and every few stitches the seam yarn is pulled snug and the two edges roll together. From the front there is simply no join — the fabric appears continuous. It takes perhaps twice as long as whip stitch and demands squares that genuinely match, because there is no ridge to absorb a difference. Save it for the project where the finish is the point.
Slip stitch: the ridge as a feature
Squares held together, hook through both edges, slip stitch along. Quick, and the strongest seam here — but it builds a solid raised line. Fighting that ridge is pointless; using it works: worked in a contrast colour on the front, it frames every square like window glazing. It also adds the most weight and the most yardage, which on a big blanket is measurable in whole skeins.
Join-as-you-go: no seaming day
Each square’s last round crochets into the neighbouring squares as it goes — corner chains and side clusters anchor into the adjacent edges. The last stitch of the last square finishes the blanket. The trade is flexibility for finality: a JAYG blanket’s layout is decided in the making, and the classic advice stands — lay every square out on the floor and photograph the arrangement before committing square one.
Notes
- Blocking before joining is the step that makes every method look better. Granny squares from the same hands still vary by an eighth of an inch, and a seam forces those differences into puckers. Fifteen minutes under a damp towel and they join like machined parts.
- Join in rows, then join the rows: complete all horizontal seams first, then run the long vertical seams straight across the junctions. The four-corner meeting points come out neater than joining square by square in a spiral, and the long seams are faster than many short ones.
- Contrast-colour joins are a legitimate design decision with slip stitch (the ridge becomes a frame for every square) and a mistake with whip stitch, where the join is meant to disappear — any wobble in a contrast whip stitch is permanently on display.
- Leave the tails from each square out of the way of the seam line and weave them in before joining, not after. A seam worked over loose tails traps them at angles that cannot be woven properly later.
- Whichever join you use, work the blanket border after all joining is done, and treat the border's first round as the tidy-up: it swallows the seam ends at the blanket edge that no join method finishes gracefully on its own.
Common questions
What is the best way to join granny squares?
There is no single best, only best-for: whip stitch through back loops for speed with a flat result, mattress stitch when the front must show no join at all, slip stitch when a raised ridge suits the design or the blanket needs maximum seam strength, and join-as-you-go to avoid a seaming session entirely. The honest default for a first blanket is whip stitch — fast, forgiving, and flat enough.
Do you join granny squares right sides together or wrong sides?
For whip stitch and slip stitch: right sides together to hide the seam on the front (the ridge lands on the back), or wrong sides together to display it as a deliberate ridge on the front. Mattress stitch is worked flat with both squares face up, which is exactly why it is the invisible option. Pick one orientation and keep it for the whole blanket.
How much extra yarn does joining granny squares take?
Measured on 4.5-inch squares in worsted: whip stitch about 0.65 yards per seam edge, mattress about 0.75, slip stitch about 1.1, join-as-you-go about 0.9 worked as part of each square's last round. A 48-square throw (82 internal seam edges) lands between 30 and 55 yards higher than the squares alone — budget 10–15% over square yardage and joining will never strand you.
What is join-as-you-go and is it worth it?
Instead of finishing every square and seaming later, each new square's final round is crocheted directly into its neighbours' edges as it is worked — when the last square is done, the blanket is done. It removes the seaming session entirely and produces a flexible join. The cost is commitment: layout decisions are made square by square, and repositioning means unravelling final rounds rather than snipping a seam.
Should granny squares be blocked before or after joining?
Before, always, when squares will be seamed — the join is a measuring device that finds every quarter-inch of size difference and turns it into a pucker. Pin each square to size under a damp towel, let them dry, then join. A finished blanket can be blocked again afterwards, but blocking cannot redistribute fabric across a seam that was sewn unevenly.