Hi Connie,
If you used my 27" x 9" for the pillowcases as you did the French Seams instructions:
For the King you need to add 10" in length overall - You could make the Main Fabric 37" and leave the Cuff at 9" but that only makes sense if you have more than a yard of your Main Fabric. Plus with a King, you would want the Cuff to be wider in proportion to the overall length of the pillow. IMOH I would suggest doing the Main at 34" with a 12" Cuff, if the Cuff Fabric is really pretty even doing 31" Main with 15" Cuff.
I agree that a pillow shouldn't be in a baby's crib until they are toddlers. If you're making a Toddler pillow for decoration or accent piece to be used later with a quilt gift then that's a different story.
Toddler/Travel pillows measure 12 by 16 inches - your pillowcase should be around 13 by 18 to 20. Main Fabric is 17", Cuff remains 9" otherwise you won't be able to turn it inside it. Might try 19" and 7" but it might be a tight turn out. Now the width of the fabric is of course to wide for this toddler pillow - 27" wide if you're doing your 1/4 French seams neatly. If you're worried then I would cut 27.5" wide for some wiggle room.
Hope this helps, Ruby
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Standard size pillows measure 20 by 26 inches.
Queen size pillows measure 20 by 30 inches.
King size pillows measure 20 by 36 inches.
Euro size pillows measure 26 by 26 inches.
Toddler/Travel pillows measure 12 by 16 inches.