The white flip flops I use are true to size.  The ivory flip flops run smaller, use chart below to dtermine your prorper size. When deciding your size, you should always have at least 1/2" space from the back of your heel to the edge of the flip flop. 

White Flip Flops - Women's flat,  and wedge sizing:

Size 5 - Flip Flop length is 9" long

Size 6 - Flip flop length is 9 1/2" long

Size 7 - Flip flop length is 9 3/4" long

Size 8 - Flip flops length is 10" long

Size 9 - Flip flop length is 10 1/4" long

Size 10 - Flip flop length is 10 1/2" long

Size 11 - Flip Flop length is 11" long.

Ivory Flip Flops

Size 5 - Flip flop length is 8 3/4"

Size 6 - Flip flop length is 9 1/4"

Size 7 - Flip flop length is 9 1/2"

Size 8 - Flip flop length is 9 3/4"

Size 9 - Flip flop length is 10"    

Size 10 - Flip flop length is 10 1/4"

Size 11 - Flip flop length is 10 1/2" 0 1/210"1/4" 11        10                        

 **If you wear a half size, then you would wear the next whole size up.