If one bedroom is bigger than the other … Divide the square footage of each bedroom by the total footage of both. So, if room A is 225 square feet and room B is 175, roommate A should pay 56 percent, or $1,792, while roommate B pays 44 percent, or $1,408.

If one bedroom has an en-suite bathroom … Tack a small amount—say 2 percent, or in this apartment’s case, $75—onto roommate B’s rent.

If one bedroom has a spacious walk-in closet and the other a standard one … Divide the square footage of the bedroom plus the square footage of the closet by the total square footage of both bedrooms and closets combined. If room A has a three-by-five-foot closet, and room B has a six-by-ten-foot walk-in, roommate A would pay 51 percent, or $1,632, and roommate B 49 percent, or $1,568.

If one bedroom has a terrace and the other doesn’t … Divide half of the square footage of the terrace, plus that of the bedroom and closet, by the total footage of both bedrooms, closets, and the halved terrace. If room A has a four-by-five-foot terrace, roommate A should pay 52 percent, or $1,664, with roommate B paying 48 percent, or $1,536.

If one bedroom has a fireplace, higher ceilings, or other amenities … “These things have character, but they won’t really change the price,” says Miller. Less than one percent—or about $25 extra a month, in this case—should cover it.