As a rule of thumb, measure around your doll's head just above the ears.  This number, in inches, is approximately what size of wig your doll will wear. 

3.5" Lati White, Sleeping Elf Mistletoe (she needs to be glued on), Real Puki

3.75" Roxy Lucy, Real Puki,

4" PukiPuki, Doll Chateau's Ada deer, Circus Kane Starr, Carrie Sawyer elf, Circus Kane Pocket size Mystery Elf, Pinch of Pepper,

4.25" Circus Kane Maheaya, Yindi, Doll Chateau Sleepy, Shoo Hoo,

4.5" Doll Chateau Beatrice, Wren, 

5" Mini Planet Dolls, Circus Kane Soda Bunny, Circus Kane Pocket Onion, BBFlocking Poppy, Jemima,

5.25" Kaye Wiggs Cinnamon

5.5" Lati Yellow, Sybarite New Generation Talc, Doll Chateau Liz kitty, Ellemino by Nikki Britt,

5.75" Pukifee, Lati Yellow,  Ellemino by Nikki Britt

6" Bobobie March is just under 6", Bambicrony Elf Shy, New Generation Sybarites,  Kimberly Lasher Lollys, Lati Yellow, Lillycat Constantine in stretch,  Ellemino by Nikki Britt, 6-7" Synthetic wigs Chae by Irreal Doll,

6.25"-6.5" Irreal doll Ino,

6.5" Doll Chateau Faust, Little Fee Ante, Doll Chateau Damara, Unoa, SoulDoll Flett, Ciao Bella Bambicrony, Circus Kane Sidone, Kimberly Lasher Willow Lolly, Lillycat Constantine, Doll Chateau Clara, Iplehouse KID Lena,

6.75" Doll Chateau Alma, Slinky Neko, Doll Chateau Alan,

7" Bobobie Ariel and Espree, Lati Green, most Souldoll Kids, Peakswoods Lady Bee, DIM Miru, Shiny Doll Meefa, Doll Chateau Bella, DIMdoll Youra, Circus Kane Nexeven, Tum, Ted, Queena by Doll Chateau, Grace by Doll Chateau, Elizabeth by Doll Chateau, Chae by Irrealdoll will wear an ooak 7" best, Tween size by Meadow Dolls, Little Stella by Connie Lowe, Little Pearl by Connie Lowe,

7.25" Hujoo

7.5" Planet Doll Riz, DIM Flowne elf, Doll Chateau Verna, Circus Kane Humpty, Ana Salvador Lucy, Soul Doll Vito Lester, Doll Chateau Lillian Unicorn, Doll Chateau Alan Elf, Nikki Britt Mini Pepper Annie, Doll Chateau Betty, Nikki Britt Adeline

8" Kim Lasher MSD elf, most Soul Doll Double girls, Lierre, Connie Lowe's Sprocket Meek, Kaye Wiggs Layla, DIMdoll Aria, Soul Doll Hye, Circus Kane Mystery elf, Circus Kane Humpty, Circus Kane Lou, Circus Kane Lemur, Ruby by Liz Frost, Ana Salvador Lucy, Doll Chateau Stacy, Kaye Wiggs Abby,

8.25"  Kaye Wiggs Layla, Kaye Wiggs Nelly,

8.5" Graceyln, Peakswoods Goldie, Dal, Byul, Kaye Wiggs Nelly and Layla in some stretchy wigs, Twigling Ingene, Shiny Doll Eeffee, Wizworks Luna, Dollstories, Kaye Wiggs Lenny, Kaye Wiggs Abby, Kaye Wiggs Miki, Smart Dolls Tibet mohair non-stretch, Cream Soda Amelia in Tibet mohair, MeadowDolls Dumpling,

8.75" DIM Trisha, Dollmore Lukia,

9" DIM Kassia, most Dollstown girls 1/3 size, Kaye Wiggs Gracie, Smart Dolls ooak stretchy wigs, Cream Soda Amelia in stretchy wigs,

9.25" Beastie by Tracy Promber,

9.5" Shiny Doll Eefee elf in handmade wigs, 

9.75" Agathe,

10" Blythe (she has the special egg shape), Meadow Dolls Lea Moppet,

11"  Linda Macario Iris, Charles Creature Cabinet Fila Moon, Connie Lowe Eppie, Nikki Britt Wendy Wierd, Tuula, Totti by Meadow Dolls, Big Pepper, 

12" Circus Kane Stadnik, Lenci, Stella by Connie Lowe, Eppie by Connie Lowe, Silvie by Meadow Dolls, 

12"-12.5" Meadow Dolls Saffi,

13"-14" Bailey by Meadow Dolls, 

14" Dollmore Lusion,

14.5" Giant Ellemino by Nikki Britt,