How do I enlarge a pattern?

I’m a beginning knitter and have just finished my first article of clothing, a v-neck pullover vest for my grandson. It’s a size 3-4, and I need a pattern in a size 7-8 for his brother. Is this hard to do? I’m wanting something that’s knit on circular needles with no seaming. Or, does anyone know of a pattern like this that’s already size 7-8? I found a website the other day that had one for sale, but of course I can’t find it now!

I think it would be a bit hard to convert that small a pattern to that large a one. One reason is that three-year-olds are shaped so much differently than 7-year-olds.

This site has lots of free patterns, and I recall a Paton’s booklet that had boys vests. You might want to take a look at their site at their patterns. :thinking:

Here’s a link to child size standards:

If you know the gauge and the measurements for the size you’re making, you can determine the number of stitches for major measurements (such as the chest). For example, for a child size 8 with a 26.5" chest and a gauge of 5 sts per inch, you’d need 132.5 sts (26.5 x 5) around the chest to fit exactly. However, since it’s a vest you’d want 1-2 inches of ease. So, the chest would be somewhere between 27.5-28.5" or 138-143 sts. Find how many stitches the pattern says to cast on and set up the following proportion:

(#chest sts size 8)/(#chest sts in pattern) = x/(#CO sts in pattern)

Cross mulitiply and solve for x. Then you’ll know how many sts to cast on.
There are many things to consider, though. If you start out doing 2x2 ribbing or a pattern that requires an even or odd number of stitches, that influences the number of stitches you cast on. If you start out with 2x2 ribbing in the round, you’ll need a multiple of 4 stitches to cast on.

Some of it is strictly math using proportions, some of it is winging it! At least for me it is. I recently re-wrote an adult pattern for a toddler starting with the chest measurement and going from there. I used proportions and the yarn standards size chart for children. Hopefully, you’ll get a lot of suggestions from many other knitters here! :wink:

Thanks to everyone for all their help! Now if I can just remember a little algebra maybe I can figure this out…

Sometimes you can fake the size change by working on larger needles with slightly larger yarn. Though it is easier to downsize than upsize I have found. I frequently change the sizes of patterns by changing the hook and yarn in crochet. It does take some playing and some courage and guessing. It also helps ALOT to have the person you are making it for readily available for frequent dress rehersals. But if you take careful measurements of ever possible angle, it is doable without the model there.

Another way, is if you are working from a pattern with multiple sizes, you can sometimes take the size differences and continue working the additions for the additional sizes. You would really only need to calculate 2 size increases (a 5-6 and a 7-8) and if the pattern is written in a way that says work until the piece measures __" start armhole shaping. Then you have it made, if you have the child’s measurements (or the measurements of a shirt they wear).

Would the same system apply for changing a hat pattern? I’m happy to do math, but I’m not sure what I should be multiplying… Thanks!