Roller Blinds are not the first choice for splay Bay Window but can be a good choice for Square Bays and Conservatories.
When measuring you must remember that the blinds cannot over lap or be bent.
One Roller Blind goes all of the way into the corner of the bend and the width of the other is shortened by the depth of the bracket.
You can find the depth of our brackets on the Bay Window measuring instructions.
Do think carefully which blind you wish to be shorter as it can make a difference to the shading and privacy provided.