Just wondering if anyone knows how you can tell how tall/big your puppy is going to be?

I did a search on the internet and for weight, I found several people/websites say times their weight at 8 weeks by 3 to get their adult weight - (in which case Rocky will probably be about 8 lbs when full grown (big for a Yorkie) but I can't find anything about calculating how tall they will be.

Thanks

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Proud owner of Rocky the Yorkie, born July 2008, who came to live with us at 8 weeks old