How big do miniture yorkshire terriers get?

It's Just Yorkshire Terrier. They are not "miniature".

They should not exceed 7lbs.

http://www.ytca.org for more on the breed.
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I own a Yorkshire and I've never heard of a miniature Yorkshire terrier
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There is no such thing as a "miniature" yorkie. There is only one type of Yorkie. http://freewebs.com/animal-education/teacups.htm

Get one from a good breeder or a shelter. http://stoppuppymills.org <- don't buy from pet stores.
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No such thing as a minature yorkie, only standard. Go to the AKC yorkie page to find out breed standard.
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according to the akc standard: Toy Group; AKC recognized in 1885.
Ranging in size from four to seven pounds, so that's pretty small.
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EDIT: oh yeah, and there is no such thing as a "miniature yorky"

there is no such thing as a "minature" or "teacup" yorkie. if you want to get an ABNORMALLY small dog prone to numerous health issues go right ahead. people who claim to breed these dogs basicly get two runts and make them mate. then they have a whol litter of little runts for which they sell for 800+ dollars. so if you want a yorkie, get a NORMAL one. standard yorkies should not exceed 7 lbs and 7 inches at the shoulder.
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Less than a foot tall, my yorkshire terrier is tiny
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There is no such a thing as a "teacup" anything unless you're referring to what is on sale at the Royal Doulton store. STAY AWAY from any "breeder" selling these undersized, overpriced, sickly runts who are shortlived. Only backyard breeders and puppy millers breed them; when a undersized dog is born in a responsibly bred litter is sold on a spay/neuter contact.

This information applies to all breeds:

http://www.ytca.org/faq.html#A
http://www.barkrescue.net/teacup.htm
http://shihtzu.org/Info/imperial.asp?menu=Info
http://www.dog-toy.co.uk/dogarticles/?article=165

Here is where you can get a happy, healthy Yorkie:

Your local animal shelters
http://www.dogsindanger.com
http://www.petfinder.org/ has MANY Siberian Huskies, mixes and Husky-type dogs in need of homes. Not all of these dogs are in safe breed rescues and no kills.
http://www.petharbor.com
http://www.1-800-pet-rescue.com
http://www.1888pets911.org/
http://www.yorkierescue.com
http://www.unitedyorkierescue.org
http://www.barkbytes.com/RESCUE/sctter.htm
http://www.google.com/search?hl=en&q=scottish+terrier+rescue&btnG=Search
http://www.ytca.org has breed info, breed rescue and responsible breeder referrals

If you are interested in a dog but live too far away from it, there is the option of having one transported closer to you/nearer to you. Google "dog rescue transportation."
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10+ years of being a shelter volunteer, pet owner and lifelong animal lover

Big enough to kick across a 12×10 room….that's from wall to the other in the air. Only about 4 feet in the air, though.
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not much LOL
oh and btw they're not 'miniture'
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There is only one size of Yorkshire Terrier. They average 5-7 lbs. With any breed, there will be specimens that are smaller or larger than average. However, any dog advertised as being intentionally smaller than average (like mini or "teacup" yorkies) means it's a poorly bred runt from an irresponsible breeder and will be riddled with health problems and most likely die very young (as in, before age 2).
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I am a breeder and my Yorkies don't get any larger than 5 lbs. I do have some that don't get any larger than 3 lbs. as well. My Yorkies are not runts and nor do they have health problems. I have tested mine and take their health very seriously. Both of my girls were the largest of the litter. My male at 2.5 lbs. was 2nd largest. They all have a clean bill of health and have never had any serious problems. I feed them all top of the line foods and money is never an issue I will give an arm and leg for my babies if I have to! I bake them biscuits myself b/c I don't like all the fillers and preservitives that are in the store bought ones. I take them on outings and socialize them with others. They all sleep with me and do wonders with my 2 small children. We all are educated in the care of Yorkies and dogs in general. I have been going to dog shows for a while now and talking to fellow lovers of the breed. I don't show though mine are too small. One of these days I might though.
There is no such thing a miniture though. There is only one standard. The wonderful thing about them is that they don't shed. I love it.
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http://www.gorgeousyorkies.piczo.com