Generally 4 cm. A quarter is hardly 2.5 cm. If the nipples are large, the areola can't be made too small or it will not look aesthetically pleasing.
Some women do have 2.5 to 3 cm areolas. Some women with small areolas have large nipples which look disproportionate, and if they want a change it is usually to request a nipple reduction.
It is desirable to have a nice proportion between the size of the breast, the nipple size and the areola size. For most women this is about 4.0 to 4.5 cm. This is particularly pleasing when women start out with 6-8 cm areolas and want them smaller. When having a lift, the larger the areola and the greater the amount of skin to be removed, the less flexibility you have in areola size if the lift is strictly peri-areolar. If you are having a vertical or inverted-T lift, then the areola can be smaller, according to the criteria above, because the breast skin can be matched exactly to the new areola. In a peri-areolar technique the larger the area of skin removed, the more difficult it is to gather the outer circle of skin down to the new areola without bunching and radiating pleats. These usually go away, but there are limits if you want to minimize the chance of a revision.
A word of caution. If the areola is made too small, it does not look good, particularly when the nipple is relatively large and fills too much of the circle of the nipple/areola complex. This is uncorrectable and leads to unhappiness with the result.