Using the rule of three to calculate how many stitches you need

And one more question. I want to follow a pattern, but I have thicker yarn and now want to use the cm measurements to figure out how many stitches I need.
To do that, you need that pesky rule of three, and I never know what to divide and what to multiply.
Is there a calculator for something like this?

In my case:
10 stitches = 6 cm
? Stitches = 72 cm 

120

Thanks ♡

So 10 × 6 ÷ 72 = 120.

Message from my big brain to my little brain: please remember that! ;-)

Anja,

Your calculation is wrong (it comes out to 0.83333).
You have to divide 72 by 6 = 12, then multiply by 10. 12 × 10 = 120.

So you divide the desired number of cm (72) by the number of cm that the 10 stitches produced (6 cm), and then multiply the result by 10.

Best wishes

Michaela

72 : 6 = 12 x 10 = 120

that would be my calculation.

I don’t know if this might help you remember it better:

I write the figures one below the other, just like you did:
10 sts = 6 cm
x sts = 72 cm
Make sure you always have the sts on the left and the cm on the right .

Then you cross-multiply :

x times 6 = 10 times 72

Now all you have to do is divide by 6 to get x.

(Admittedly, it’s a bit mathematical, but I can remember it really well this way!)

Thank you so much, everyone—I meant to write it differently but ended up typing it the wrong way around.... 

Hi Anja

It’s even easier with a knitting calculator (conversion table) — you can just look up the desired number of stitches. But I also need the rule of three every now and then, and I do it the same way as ruthk.

So I calculate 10:6 × 72

*laughs*

There are many ways to get there ;)

Since multiplication and division are of equal rank, the order in which you do the calculation doesn’t matter. In other words, it doesn’t matter whether you multiply by 72 first and then divide by 6, or divide by 6 first and then multiply by 72.

This might make it a bit clearer....

If you need 10 stitches for 6 cm and want to know how many stitches there are in 1 cm, divide 10 by 6....

Then take that result—with all its decimal places—and multiply it by the size you want to have—so here, the calculated number of stitches × 27 cm—and that gives you your result.

For me, this is the easiest way to follow and also the most logical way to explain it....

Claudia, that's my thinking too: first I need to know how many stitches there are per 1 cm. The problem with that: often the numbers you get for calculating are “impractical,” i.e. with lots of decimal places. 
So once again my advice: use a knitting calculator; it measures 10 cm…

What is a knitting calculator?

There’s also a chart available for purchase here...

So I Googled “knitting calculator”.... Since I rarely need this, it’s probably not worth buying one. I’ll just look for the chart here instead. Thanks, Ruth!