Hi!
If you want to measure your bra size you can use a tape measure that measures in inches. Wear your post op bra and measure under your boobs nice and snug, if it measures in between numbers round to the nearest whole one, add 2 inches and that’s your band size. Then measure your boobs round the fullest part, usually across the nipple. Don’t measure too tight, make it a little looser, round that measurement to the nearest whole number. Subtract the band measurement from the boob measurement. 1in=A 2=B 3=C 4=D etc.
This should give you some idea but just remember at 8 days you are still going to have a lot of swelling underneath and on the boob so it’s going to effect the difference and therefore the cup size you work out. It also will effect what you see in the mirror!! So don’t get too obsessed with their size just yet, they really will start looking fuller and more like what you expected over the next few weeks as the swelling goes down and they start loosening in the pockets!
Hope this helps a reassures!