Start with yarn weight and a gauge swatch

Before you cast on for a full sweater, you need to know two things: what yarn you are using and how tightly you personally knit. The yarn label tells you the weight (how thick it is) and the recommended needle size. A yarn labeled "worsted weight" or "DK weight" will knit at a predictable speed and drape the way a sweater should.

Next, knit a gauge swatch—a small square about 4 inches across in the stitch pattern your sweater pattern calls for, using the needle size the pattern recommends. Wash and dry it the way you will wash the finished sweater. Then measure how many stitches and rows fit in 4 inches. If your gauge does not match the pattern's gauge, your sweater will be the wrong size. Adjust your needle size up (if your stitches are too tight) or down (if they are too loose) and knit another swatch until it matches.

Key Takeaways

  • A gauge swatch tells you whether your needles and yarn will produce a sweater the right size; skipping it is the most common reason a finished sweater does not fit.
  • Most sweater patterns are written for you to knit the body flat in pieces (front, back, sleeves) and seam them together, or in the round as one tube from the bottom up.
  • Cast on for the back or body piece first, knit straight up to the armhole, then decrease stitches to shape the neck and shoulders before binding off.
  • Seaming takes as long as knitting; use a yarn needle and a whip stitch or mattress stitch to join pieces so the seams are nearly invisible.
  • Picking up stitches around the neckline and knitting a ribbed collar finishes the sweater and hides where the pieces meet.

Choose a pattern and gather your materials

Pick a sweater pattern that matches your skill level. A beginner pattern uses stockinette stitch (knit on the right side, purl on the wrong side) and straightforward shaping. Intermediate patterns may include cables, colorwork, or more complex decreases. Read the entire pattern before you start—do not just skim the first page.

Gather the yarn in the amount and color the pattern specifies. Buy slightly more than the pattern calls for if you can, because dye lots vary and you may need to adjust the fit. You will also need needles in the size the pattern recommends (usually two circular needles or one long circular needle for knitting in the round, or straight needles for flat pieces), a yarn needle for seaming, stitch markers, and a measuring tape. Some patterns call for a cable needle or double-pointed needles for the ribbing at the cuffs and hem.

Knit the back and front pieces

Most sweater patterns have you start with the back piece. Cast on the number of stitches the pattern specifies. If the pattern calls for ribbing at the hem (usually 1 to 2 inches of knit-1-purl-1 or knit-2-purl-2), knit that first. Then switch to stockinette stitch and knit straight up until you reach the armhole depth marked in the pattern.

At the armhole, you will bind off a few stitches at the beginning of the next two rows to create the opening for the sleeve. Then, on every other row, decrease one stitch at each edge (usually by knitting two stitches together) until you reach the width the pattern specifies for the shoulders. Knit straight until you reach the neck depth, then bind off the center stitches for the neck opening. Knit each shoulder separately, decreasing at the neck edge on every other row to shape the slope, then bind off.

Knit the front piece the same way, but bind off the center stitches for the neck opening earlier (usually 2 to 3 inches before the back). This creates a deeper neck. Shape each shoulder the same way as the back.

Knit and attach the sleeves

Sleeves are usually knit flat from the cuff up, or in the round on a circular needle. Cast on for the cuff and knit ribbing the same depth as the hem. Then switch to stockinette and increase one stitch at each edge every few rows (the pattern will tell you exactly when) until the sleeve reaches the width you need at the upper arm.

Knit straight until the sleeve reaches the armhole depth of the body. Then bind off stitches at the beginning of the next two rows the same way you did for the body armhole. Decrease at each edge on every other row until you have only a few stitches left, then bind off. This creates a cap that fits into the armhole opening.

Lay the body pieces on a flat surface and pin the sleeves into the armholes. Use a yarn needle and whip stitch or mattress stitch to sew the sleeves in place. These stitches run along the edge of the knitting and are nearly invisible when done correctly.

Seam the pieces together

Lay the front and back pieces right-side up on a flat surface. Thread a yarn needle with a length of yarn (about an arm's length). Starting at the bottom, insert the needle under the edge stitch of one piece, then under the corresponding stitch on the other piece. Move up one row and repeat, pulling the yarn snug every few stitches so the seam stays tight and flat.

Work up both side seams this way. Then seam the underside of each sleeve to the side of the body. The mattress stitch, which runs between the edge stitch and the next stitch in from the edge, creates a seam that is almost invisible from the outside. If your pattern calls for it, seam the sleeve caps to the armhole opening the same way.

Pick up stitches and knit the neckline

The neckline is usually finished with a ribbed collar that you knit by picking up stitches around the neck opening. With the sweater right-side up, insert your needle under the edge of a stitch at the base of the neck and pull yarn through to create a new stitch. Work around the entire neck opening, picking up roughly one stitch for every row on the sides and one stitch for every bound-off stitch across the front and back.

Once you have picked up all the stitches, join them in the round (if using a circular needle) or knit back and forth (if using straight needles). Knit ribbing (usually knit-1-purl-1 or knit-2-purl-2) for 1 to 1.5 inches, then bind off loosely so the collar does not pull. Weave in all the loose ends with a yarn needle.

Block and finish your sweater

Blocking sets the shape of your sweater and evens out the stitches. Wet the finished sweater in cool water with a small amount of wool wash (or gentle detergent), squeeze out the water gently, and lay it flat on a blocking mat or clean towel. Pin the edges to the measurements given in the pattern and let it dry completely, usually overnight.

Once dry, try on the sweater. Check that the armholes sit at the right place on your shoulders, that the sleeves reach your wrist, and that the length is what you want. If the fit is off, you can usually adjust it slightly by blocking again to a different measurement, but major changes are difficult once the sweater is seamed.

Frequently Asked Questions

What if I make a mistake several rows back?

If the mistake is small and does not affect the fit, you can often leave it—no one will notice once the sweater is worn. If it affects the stitch count or shaping, you will need to rip back to that row, fix the mistake, and knit forward again. This is called frogging. Use a smaller needle to pick up the stitches as you pull the yarn out.

Can I knit a sweater in the round instead of in pieces?

Yes. Top-down sweaters are knit from the neckline down as one tube, with increases for the armholes and decreases for the neck. Bottom-up in-the-round sweaters start at the hem and work up. These methods avoid seaming but require circular needles and are usually better for intermediate knitters.

How long does it take to knit a sweater?

A straightforward adult sweater in worsted weight yarn takes most knitters 40 to 60 hours of actual knitting time. That translates to anywhere from two weeks to two months depending on how often you knit. Seaming and finishing add another 5 to 10 hours.

What should I do if my sweater is too big or too small after blocking?

If it is only slightly off, blocking to a different measurement may help. If it is significantly wrong, you can unravel it and reknit it with a different needle size, or accept it as a learning sweater and start again. This is why the gauge swatch matters so much.

Do I have to weave in all the ends before wearing it?

Weaving in ends before blocking is easier because the sweater is flat. If you wait until after, the ends are harder to hide. Loose ends can also catch and pull, so it is worth doing before you wear the sweater.