Bentley House Minis really gets into the subject of scaling in the following Youtube:
https://www.youtube.com/watch?v=M_ooX1aXGFk

Joanne has a Youtube that demonstrates scales:
https://www.youtube.com/watch?v=a2rv4HCsaOM

However, neither the above mentions 1:3 scale, which I call Girl Doll scale. That category includes such dolls as American Girl and My Twinn. I tend to include any doll that is 16"-20" in that range.

There's also another factor when considering scale. That is the thickness of the doll, i.e., is she a 12" chubby little girl or a 12" adult woman. A cookie should look bigger in a little girl's hand than in an adult's hand. Yet a Barbie has tiny hands compared to her height. Sometimes you just have to use your mind's-eye to determine what will work for your situation.

By the way, I prefer to use the ratio symbol when expressing scale. For example. 1:3 instead of 1/3. The following might be a good visual for you. I don't know the author in order to give credit. Though the doll 2nd from the left is technically 1:12 scale, she would tend to look out-of-scale in a standard dollhouse.

Here's my rule of thumb:

1:3 Girl Doll Scale
This scale includes young girl doll sizes 16"-20". There are also some tall fashion dolls that would be included in the 1:3 category.
1:6 Fashion Doll/Play Scale
12"-14" (approximately) Barbie type dolls and girl play dolls
1:9 Hitty Preble Dolls
The original Hitty doll is a 6.25" girl style doll. Thicker body than say a 6" dollhouse doll. She's considered a girl rather than an adult...although she does get dressed as a bride. Hmmmm.
1:12 Dollhouse Scale
This is standard dollhouse scale. For every 12 inches in the real world, 1 inch will do in the dollhouse world. A 6 foot real man should be a 6 inch tall man in the dollhouse.

1:24 is Half-inch Dollhouse Scale
That 6" man in the 1:12 Dollhouse should be 3" in the half-inch dollhouse. When speaking of 1/2" dollhouse scale I express it as 1:24, using the ratio ":" symbol instead of 1/24. That helps eliminate confusion. I have a couple of projects at this scale. It's just too small for me to make the proto-types, so I don't intend to add any more at this scale.

1:48 is Quarter-inch Dollhouse Scale
This is itsy-bitsy and way to small for me to design. I do have some dollhouses that would be considered 1/4" scale, but I can't design the furniture. This scale is more impressions of things rather than exact replicas.
   

18" American Girl Doll with 1:6 scale Eloise Wilkin book	12" Antique French Fashion Doll with 1:6 scale Eloise Wilkin book	12" Fashion Doll (thicker than Barbie) with 1:6 scale Eloise Wilkin book
6.25" Hitty Doll with 1:12 scale Eloise Wilkin book	8" Betsy McCall Doll with 1:6 scale Eloise Wilkin book	12" Fashion Doll (thicker than Barbie) with 1:12 scale Eloise Wilkin book
	8" Betsy McCall Doll with 1:12 scale Eloise Wilkin book

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