Converting gauge/size/yarn amount

Hi everyone!

I’d really like to finally crochet a real garment, namely a cardigan. However, since I’ve never done this before and have never worked with a gauge swatch, I’m not sure how to go about it. I’ve picked out a yarn, but it’s thicker and has a shorter yardage than the yarn in the pattern.

Yarn in the pattern:
175 m per 50 g, hook size 3.5 to 4 mm
Chosen yarn: 115 m per 50 g, hook size 4.5–5 mm

For the cardigan in size L, I need 320 grams/1,110 m (7 skeins) of the yarn mentioned above. Is there a way to convert this based on the information provided, or what else do you need for that? Sorry, I do crochet a lot, but only scarves, shawls, headbands, etc.—all things where I can get around making a gauge swatch, and I’ve always just estimated the yarn amount so far.

Thanks in advance and best wishes
Saskia

You’ll need roughly the same meterage, which means about 10 balls. You can calculate that using the rule of three: 115 m equals 50 g, so 1,110 m equals 483 g—which is about 500 g.
To figure out the number of stitches to cast on, you’ll also need to use the rule of three.

Or you can check out Traudelina’s shop here: she’s put together some great tables where you just have to enter the values.

Thank you so much, ruthk—that definitely helps! :D
Best wishes
Saskia