How many stitches should i cast on?

Hello everyone
I’m still a novice, i’ve been knitting since Christmas and i’m loving it, loving it, loving it.
But i would really like your expert advice please on my next project.

I’ve made a few hats, and i’ve just guessed at how many stitches to cast on, via guesswork and swatches, sometimes they come out ok, and other times they are a little too big or too small.

I’d quite like these hats to be perfect(ish)
I am making two hats for my friends out in NZ, it will be winter when it is their birthdays in June.
I have some rather lovely green wool, one shade Olive and the other Fern and i want to knit both yarns together, i’ve done a swatch and it looks lovely.
(i could post a pic up if i knew how)

If i was knitting with just one ball of yarn it recommends using 4mm needles, and obtaining a gage of 22st and 30rows measuring 10x10cm

Details of the swatch i did with both yarns are, i used size 6mm needles, i cast on 20 st and knitted for 21 rows of a mixture of plain and ribbing (i wanted to see the difference between the two in width).
It measures 13cm across on the plain stitches and 12cm across on the ribbing.
It measures about 12cm in height.

My friends head measures 59cm and her son measures 50cm.

if i double my gage it works out like this.
6.5cm 10st
13cm 20st
19.5cm 30st
26cm 40st
32.5cm 50st
39cm 60st
45.5cm 70st
52cm 80st
58.5cm 90st

therefore i could cast on 90st for the mum and 78, 80st for the boy.

what do you think, you advice will be very much appreciated.


This site should help.

Yes ribbing pulls in which is why it’s used for cuffs, to snug up the hat/sock/sweater. If you want to use the 6mm, take the number of sts per inch times about 20 or 21 inches (uhh that’d be around 50-52cm) and CO that many sts. That should fit most adult heads. And Ingrid’s link should help too.

I also like this site:

i would cast on less than that.
dont forget that ribbing stretches. so the 12cm of the swatch is it unstretched and in this state would just be sitting un the head with little grip.
you would need to make it smaller to give the ribbing a chance to stretch and to hug the head proprly otherwise the hat would be too loose.

I would suggest measure in the ribbing stretched out fuly and seeing what the difference is so oou get an idea of how much give there is.

for example. if it measure 12cm unstretched and 14cm fully stretched then iwould probably take 13 cm as the measurement (mid way between the two).
so sons head is 50cm divide this by 13cm you get 3.8cm. multiply this by the number of stitches in the swatch (20) you get 76.

ok with my guesses at guage your estimate was pretty spot on, but that is the sort of measurement and calculation i would use

Thank you very much for all your advice.

Ingrid, that formula is very good, already bookmarked, i worked it out and it came out as
Mum - 88, then increase 2 before decreasing.
son - 80 st
so i was basically spot on, which surprises quite a lot, i’m not usually accurate.

Suzeeq, your formula works almost exactly the same as well, cheers.

Candicane, that link looks really good, i’m gonna bookmark that one.

tarrentella, thank you for your formula, that one is duly noted as well and very glad it has come out similar.

brilliant, thank you so much.

Fab Formula

Mum - 88, then increase 2 before decreasing.
5" - 20st
A = 4 st
B - 22"
c = 88 / 90
d - -2 to get 88
e - 2

Son - 80 st
5" - 20st
A = 4 st
B - 20"
c = 80
d - 80
e - 0