eSplitter is handy tool for sharing expenses from your Windows Phone. Whether it's divvying up the cost of dinner out, splitting the cost of groceries or splitting up the cost of supplies for a party. The app not only tracks the expenses but also keeps a running tally for the participants involved in paying for things. You can divide the expense by portions or divide the expense total equally amongst everyone involved.
eSplitter is available for both Windows Phone 8 and 7.x devices. The interface takes a little time to get used to but if you need a solution to determine costs, eSplitter is worth a try.