I believe CLs are sized in French sizes (a French 40 is not the same as a Italian 40). Then, the fit of CLs can be very vary greatly from style to style, which adds to the confusion...
Here is my experience.
I hope it helps those in need of advice.
Caracolo +1,
Size up a whole size
City Girl Sandals +1/2,
Size Up a half size
Clichy 100mm (Patent) +1,
Size Up a whole size
Declic 100mm & 130mm +1/2.
Size Up a half size
Decollete 868 Jazz Black +1 1/2,
Size Up a size and a half
Decollete 868 Jazz Taupe +1,
Size Up a whole size
Decollete 868 Paillete +1,
Size Up a whole size
Lady Gres Leather +1,
Size Up a whole size
Lapono Patent +1 1/2 or 2,
Size Up a size and a half (or two sizes)
Mad Mary +1 or 1 1/2,
Size Up a whole size or size and a half
Minibout Zep +1/2,
Size Up a half size
Metallika Boot +1 or 1 1/2,
Size Up a whole size (or a size and a half)
New Simple Pump +1/2,
Size Up a half size
Numero Prive +1/2,
Size Up a half size
Pigalle 85mm Mesh +1/2,
Size Up a half size
Pigalle 120mm Patent w/ Straight Heel +/-,
True to size
Pigalle 120mm Blue Leopard Patent +1/2,
Size Up a half size
Rolando (all fabrications) +1 or 1 1/2,
Size Up a whole size (or size and a half)
Simple Pump +1/2,
Size Up a half size
Som 1 100mm +1 1/2,
Size Up a size and a half
Very Prive +1/2,
Size up a half size
Yoyo 85mm +1,
Size up a whole size
Yoyo 110mm +1,
Size up a whole size
Please note: this is my personal experience, and everyone's feet and fit will vary.
I tend to go a little bigger than some.
Good luck!