Granny Stripe to 145cm keeps growing! Why?

[Littlemissn10]

I have pulled this thing apart a bajillion times! Send help! 
I’m trying to crochet granny stripe back and forth across a measurement of 145cm (must be this length to fit it’s location). 
I work the chains, then a row of DC and then a row of Tr skip 2 chains etc.  it appears to be growing by 10cm each row!  Why?

Any help would be appreciated.  
Regards, Danielle

[Granny Square]

Are you working from a pattern, or just winging it?  (I think you are using UK terms, I'll stick with that)

Have you counted your stitches?  And whoa! 10 cm just 'sunk in', that is 4" each row, I think you have set a record but not in a good way!  Can you take a photo and post it here?  (when you are in posting mode, there is a spot at the bottom of the box you type in that says" drag files here"...)

What you are describing would be netting, not a granny-style stitch.  A 'granny stitch' is typically *3 UKTR into 1 space, chain 0, 1 or 2 (it varies), repeat. If you are making it flat, rather than center-out in the round like a granny square, the odd rows MUST be different (offset) from the even rows. 

I will see if I can find a "real" pattern, for you to follow, back in a bit.  A trick for something with a short repeat like this, since you need an exact measurement of 145 cm, make a chain longer than that.  Work back across until you 'hit' 145cm, leave the extra chain dangling.  Later, you can pick the extra chains out, they won't unravel from the knot end.

Edited June 6, 2021 by Granny Square

[Granny Square]

Typical granny stitch-style done in rows - https://www.maggiescrochet.com/pages/stitch-repeat-granny-rows-free-crochet-pattern

It's only a 2 row repeat, which is what I meant by odd rows must be different than even rows.