I have, what seems to be, a ridiculous problem! I have been crocheting for decades! I live in UK and am perfectly familiar with US terminology. My problem seems to be yarn related- but could be anything! I purchased a filet crochet pattern via Etsy from a Canadian seller. The pattern gave measurements for Cotton yarn/thread no 10, 20 and 30. I had some spare 20 and used that. Despite using a 0.60 mm crochet hook, the thinnest I have, (the pattern suggested the equivalent of a 1.25mm) the starter chain row turned out nearly 2x as long as required by the pattern. I contacted the writer of the pattern and she could not explain why - other than to suggest that Canadian yarns/threads are different in size. I went onto a Canadian website - and they look absolutely identical to what I am using - that is clearly labelled 20 and is even called TWENTY! Please, please - has anyone any suggestions?
What is the name of the pattern? Contacting the designer was a good idea.
Even though it sounds like the pattern is written for the no. 20 thread, I wonder if you can try a thinner thread?
Is it worth proceeding on with the pattern in an effort to see if the item works out albeit in a bet larger size?
Is it possible that the size given for the starter chain is incorrect?
Hi.
Thank you for replying.
The pattern is Golden Retriever dog filet crochet pattern. The designer just said she had never had this problem before and refunded my money!
I have continued with the pattern, in 20 as I donāt have any 30 thread, but instead of the starter chain measuring c 17 inches, it measures 28! As there are only 73 rows to the pattern I think I would end up with a dachshund instead of a golden retrieverš.
I donāt believe here is a problem with the size given for the starter chain a) because I mentioned the measurements to the designer and b) because the pattern clearly shows the horizontal and vertical measurements!
What I am trying is repeating every row - which I hope will make it more proportionate. Do you have any comments about that? I think itās about all I can do at the moment!
Perhaps @OffJumpsJack or @Snowfleas can help.
Hi Felicityjg;
Is the pattern written only or is there a chart that goes with it? If there is no chart, I would get some graph paper and transfer the stitches onto the graph paper to see what the finished pattern is going to look like. Doing double rows could make it very odd looking.
I have worked with filet crochet before and even designed my own projects using graph paper. There is a lot of math involved but it is well worth it when the piece is finished. Basically, you will need, for each square, four stitches or chains. In the next row, the first chain is used for a āchain four to turnā which is equal to your first double crochet. The second and third chains will be below a chain two space and the fourth chain is for another double crochet. To fill in a square, you do a double crochet into a double crochet, then a double crochet in each of the two chain stitches followed by a double crochet into the next double crochet.
Doing a practice piece is important to know your gauge. Chain four for the first square and then chain three for each additional square across your work.
Once you know how many squares you get to the inch you can decide on the width of your project. Transfer your idea onto graph paper. When I did a bedspread, I had to tape many sheets of graph paper together.
It might sound difficult but once you do a small piece the larger ones are much easier than you would guess. I would start with a square or rectangular doily with a solid diamond in the center. You could also do a square with a checker-board pattern. Just fill in every other square and on the second row, leave each square open that is above the solid ones. Reverse each row until it is big enough. You could do a small baby blanket and trim it with a scalloped edge. I hope this is helpful. Your pattern sounds very interesting.
Good luck;
Vicki Henderson
I can not imagine using 0.6 mm crochet hook 
since mechanical pencil lead ranges in similar sizes of 0.5, 0.7 or 0.9 mm.
I also know that special crochet hooks are needed for crochet threads smaller than finding and lace weight yarns. I did not know how or if the UK sizes are different from US sizes but suspect the hook size is not what you think it is. 
Crochet threads get smaller as the number increases. 3 is the largest. 5 is thinner. 10 is about half of size 5.
Here is a video about crochet threads and the special steel hooks to use with the threads.
YouTube? Kmapp=desktop&v=cnX4xH_pwf0
So I would say check with your local yarn or fabric/sewing stores, or with friends or family.
Hi
Thank you so much for taking the time to reply! Actually, the 0.6mm hook isnāt too bad to use!! I would have thought that mm would be the same in any language? (although I do know American teaspoons donāt measure the same as British ones!) The pattern recommended a steel crochet hook US size 9 for no. 20 crochet cotton - which, when I googled it for conversion to UK sizes came up at a 1.25mm which is where I started, gradually reducing the size to try to get the right gauge. I have been crocheting for decades 
and have used crochet cotton many times with no problems at all. but this one has just defeated me for sizing! Unfortunately none of my friends or family crochet - and Iām not sure our stores (even if they were open - weāre in lockdown) could advise on whether Canadian mm are different from UK ones! I think theyād just google it like I did. I put the question of this forum as a last resort and I really appreciate your trying to help - but I think I just have to admit defeat!
Hi Vicki
Thank you so much for your really detailed reply. The pattern was chart only, with the same measurements given for 6 different threads and yarns from crochet cotton no.5 through to worsted weight - with recommended hook sizes for each. The recommended steel hook was a US size 9 which converted to 1.25mm - so I kept going down sizes to see if I could get the tension/gauge correct.
I have also worked in filet crochet several times and never had this problem before! I so admire you designing your own projects, but I am not sure that I am going to want to spend time designing a golden retriever with a border (which is what this is!) Getting that gauge right might defeat me! The pattern came complete with the diagrams for each block which I double checked, just in case I had forgotten - but everything was fine there. The problem lay in that the starter chain of 220 was about twice as long as it should be, but the stitches were small and so the picture would have been squashed (There are only 73 rows to the pattern). The designer gave detailed measurements to the side of the chart - so that is not in dispute - it is just that, for some reason, my chain is far far too long! She could not understand why and refunded my money (which was very kind)
Again, thank you so much - I will see what happens after a few rows of doubling - but I think you might be right.
Felicity
Hi Felicity;
I really hope it turns out right for you. Does it look right on the chart? Are the spaces on the graph paper in perfect squares or are they more the shape of a rectangle that is taller than it is wide? Do you have a link where I can go to see the chart? Donāt post it here though. I get frustrated when I canāt figure out a solution to a problem. I keep trying to figure out why the pattern is not working for you. Please let me know how you get along with this.
Vicki
I found this site with some details of the finished sizes based on thread size.
I have some number ten crochet thread. I placed it across my ruler and it seems round about one mm thick thread. I do not have any #20 thread to compare it with.
My number 9 steel hook is 1.40 mm and I have chained about 5 inches and counted the tiny little buggers (since I had to get out my magnifying glass, boy my eyes have not aged well).
My gauge was 36 ch per 10 cm or 3.6 sts per cm (9 per in).
your gauge is about 8 per inch (7.8 per inch
Ah, okay what stitch are you using on your second and following rows?
Since the pattern I found uses inches I will assume the Crochet terms are also US and not UK terms.
Make the stitches larger by one more āwrap yarn round hookā before starting.
My guess is the pattern says Double Crochet and you should then use a Treble.
A US Treble is equal to a UK Double treble crochet.
etc.
Switching to a taller stitch will make your rows taller without having to make double rows.
Why? not Double rows?
Well, the solid cells may turn out square with double rows or they may be slightly taller (rectangles) while the empty cells will still be short and wider and stacked. The empty cells will no longer be empty and instead have the chain running horizontal through them and muddy the image by filling in some of the negative space of the empty cells.
You can take your second ball of thread and crochet a swatch that is 10 cm across and see what stitch it takes to make nearly square cells in your swatch.
Change ādoubleā in the following quote from from Snowfleas to read as āTrebleā (or maybe double treble - DTC in UK terms):
To fill in the first square, you skip [three] chains and Treble Crochet (UK) into the [fourth] chain from the hook each of the next three chains.
Now in the image I see in the linked page above to an etsy site having the exact same pattern name I count about 73 squares in the first row to be worked into the starting chain. (you also stated you have 73 rows to work in the patern, hmm? 
)
Using 4 chains per square, plus 3 chains comes to 295 ch. (too wide)
So the pattern must be calling for 3 ch per square (later 3 TC per square).
My sample chain was rather squashed with DC (TC in UK) and 4 chs or sts per square. 
Have you made a TC swatch to check for squareness of your square using this stitch?
If they remain short try a double-treble DTC or larger stitch to make the squares as tall as they are wide.
Good luck with your pattern. The sample images for that pattern are attractive.
Please show us your finished project.
Thank you both SO much - this is such an interesting chat -
I have just measured my thread and it is less than 1mm thick.
The pattern suggests a size 7 hook for #10 thread.
I have just conducted an interesting experiment - I crocheted a five inch chain with my #20 and a 1.40mm hook - the first time I saw that the chain was quite loose - and it was c38 chains to the 5 inches, the second time I made a much tighter chain and it was 49 chains.(I got around counting the chains after making them by carefully counting an measuring at the time!) Then with a 1.00mm it was 53 chains.-
The gauge given in the pattern is 10 squares to 2.3 inches or 10 rows to 2.5 inches. - obviously for all the yarns - the idea is just to change to hook.
Iām afraid all this maths is getting to me!! Iām extremely literate and can do maths - but numbers just terrify me!
However, it all looks as if I am still way out on that starter chain - even if I use the smallest hook and tighten my stitches.
In reply to the next part - I am using what we call treble stitch - I follow US pattern all the time with absolutely no problem - even really complicated ones!
Thank you for explaining why I shouldnāt double up the rows - that makes sense.
In reply to Vikki - my squares are pretty square - I really like the idea of a double treble stitch (UK) but I think it will make it might the squares more rectangular!
Using 4 chains per square, plus 3 chains comes to 295 ch. (too wide)
So the pattern must be calling for 3 ch per square (later 3 TC per square).
The pattern says each solid square is 4 DC or each open square 1 DC followed by 2 chains and 1 DC - obviously the DCs forming the edges of the square and crocheted into the row below DC.
I will try the double treble stitch and see what happens and let you know.
In fact, I will probably be putting this to one side for a while as a friend has asked me to make her a long line cardigan and that yarn arrives tomorrow. I only crochet/knit in the evenings for a couple of hours whilst watching TV .
Thank you so much - I will try tightening the starter chain and using DTC initially - task for tonight!
People are so helpful here - 
Felicity
Ah, I missed out the important numbers!
I meant to say this.
73 squares time 3 chains each, plus one to finish the last square equals 220.
Each square shares one stitch with the next square.
Thank you. Yes my stitch count is accurate - I have 220 stitches all thatās wrong is the starter chain length!!
Felicity.
Sorry I should have said my stitch count for the squares etc is correct! I still just have no idea why the starter chain is so long! If I could get 220 starter chains to be about half the length they are - I would have absolutely no problem. I have made many
filet crochet items so understand the concept of the blanks and blocks. Itās very frustrating!!
Felicity
The mm being the same is probably the only thing you can really count on. That is a standardized metric measurement. Beyond that, Iām as lost as you are, or maybe more so. Good luck getting this untangled!
I just have to say as a Canadian how frustrating it is sometimes, I have a British crochet book for the North America market so it does use American terms but gives measurements in both imperial and metric. Metric is the same everywhere my 25 mls is the same as yours and so our tablespoons are the same but I completely ignore the difference when using American recipes but works for cooking doesnāt for knitting. Whatās even more fun vintage patterns with pre metric Canadian or British needle sizes.
I am glad that she refunded you!
Indeed! Yes - but I so wanted to make the pattern!! Iām pretty bi-lingual with patterns and recipes! I have American cup measuring jugs - my American friends say our system is so much easier and so much more precise! But then, my grandmother never weighed anything - it was a bit of this, a bit more of that!! 
.
I learned to knit with the old imperial measurement needles and hooks - I have to say I can hardly remember them now -
Although I have plenty of them! I tend to use wooden needles for knitting now - but still use metal hooks - much prefer them to wooden ones.
Fortunately - all information is now available online - so I just google anything Iām not sure about re needles, yarn terminology etc.
It is also funny but Canadians as a rule donāt weigh when cooking, metric measurements but no scale so neither British or American cook books are good fortunately published for Canadian market is a thing there.