Remember, the "sizes" given in knitting patterns are only approximations. Any knitting pattern worth its salt will give you "Finished Measurement" as well. This is the actual size of the finished garment. Go by Finished Measurement.
Your 3-month-old baby may be a dainty 16" around the chest, while my 3-month-old baby may be a hearty 19" around. So while the Momogus Knits 0-6-month size (20" Finished Measurement) would fit your baby comfortably, I should make the 6-12 month size (22" Finished Measurement). A good rule for babies and kids: When in doubt, make the bigger size. They will always grow into a bigger sweater; they won't ever get smaller.
For older kids and adults, the best way to figure out what size to make is to measure a sweater or sweatshirt they like. Lay it flat on a bed or table and measure it from armpit to armpit. Double this and you get the "Finished Measurement."
For hats, go down 1-2" from head circumference when choosing which size to make. If you make a hat with the same circumference as the head involved, it will be big and droopy instead of snug and warm. In other words, if your baby has a 16" head, make a 14" hat.
Ease is the amount of space between you and your sweater. Broadly defined, if you have a 32" chest: a sweater with a finished measurement of 32" will be skintight (0" ease), 34" will be close-fitting (2" ease), 36" will be neither tight nor loose (4" ease), 38" will be oversized (6" ease).
Your skinny 13-yr-old son may have a 28" chest, but loves gigantic sweatshirts. Make him a sweater with at least 6" of ease.
What yarn should I use?
Momogus Knits babies' patterns all call for yarn that gets 5.5 sts/1" — usually a sport or dk weight. Machine washable wools, cottons or blends are very popular with frazzled mothers. Choose yarns that are soft, and don't feel you have to use "baby" colors. Clear bright primary colors look great on babies too. And if the parents are particularly hip, choose an offbeat color, like tangerine orange or lime green.
Momogus Knits kids' patterns all call for yarn that gets 5 sts/1" — usually a worsted or light worsted weight. Again, machine washable wools, cottons or blends are great — especially if your child, like mine, wears his sweater outside like a coat and then rolls around on the ground, picking up chalk, bubble liquid, mud, grass, bird seed, crackers, and whatever else is around.
Momogus Knits adults' patterns all call for yarn that gets 4.5 sts/1" — usually a worsted or aran (heavy worsted) weight. Use machine washable yarn if you're knitting for someone who'll throw all his or her clothes in the laundry together (think college student). For more laundry-responsible adults, the sky's the limit.
What's a gauge swatch? Do I really need to make one?
No, you don't have to make a swatch…unless you want to be sure that your garment fits! Yes, a gauge swatch can be a pain in the neck — you have the yummy yarn, you have the perfect pattern, why can't you just start? The pattern is telling you what size needles to use — why do you have to make a gauge swatch?
Here is one of the most important things you can ever learn as a knitter: The needle size given in patterns is only a suggestion or starting point; however, the gauge given in a pattern is not a suggestion — it is written in stone. Each time you use a new yarn in a new pattern, you really really should make a gauge swatch [I hesitate to say "must" because I try never to say "must" in knitting; let's just say I strongly urge you to make one]. A gauge swatch gives you the peace of mind of knowing that the garment you've just spent weeks or months sweating over will fit, that it will be the same size that the pattern told you it would be. You don't have to fret as you knit, worrying that maybe it looks really small or really big.
Every knitter knits differently — some knit loosely, some tightly, some "just right." Three different knitters using the same yarn, the same needles, the same number of stitches will produce three different sized swatches. This is why it is important to make a gauge swatch before you start.
Okay then, I'll make a swatch — how do I do it?
Here's how to make a gauge swatch: If the gauge given in a pattern is 20 stitches to 4" (which is also translates to 5 stitches to 1") in stockinette stitch and the recommended needle size is Size 8, then by all means start your swatch on a Size 8 needle. Cast on 20 stitches with the yarn you plan to use for your project and begin working in stockinette stitch (if the gauge was given in garter stitch or a cable pattern, then that is what you would work your swatch in). Work as much as you can stand – the bigger your swatch, the more accurate it will be. When it measures 3" or 4" long, lay it flat on a table and measure the swatch width-wise right under the needles. Don't cheat and stretch or squeeze — take an accurate measurement!
If your swatch is 4" wide, congratulations! You may start your project. You are getting 20 sts to 4" on a Size 8.
BUT, if your swatch is wider than 4", you are getting too few stitches to the inch and you need to go down a needle size. Find a Size 7 needle and keep going in stockinette. Continue to go down needle sizes until your swatch is 4" across. If you need to go down to a Size 1 to get 20 sts to 4", then that is the correct needle to use.
If your swatch is smaller than 4" wide, then you are getting too many stitches to the inch and you need to go up a needle size. Find a Size 9 needle and keep going in stockinette. Continue to go up needle sizes until your swatch is 4" across. If you need to go up to a Size 15 to get 20 sts to 4", then that is the correct needle to use.