With Solver, you can find an optimal (maximum or minimum) value for a formula in one cell - called the objective cell - subject to constraints, or limits, on the values of other formula cells on a worksheet. In Excel, Solver is part of a suite of commands sometimes called what-if analysis tools.
This web eBook provides Help for the basic Solver included with Excel (all modern versions from Excel 2010 onwards), and for the Solver add-in available for Excel Online in Office 365, SharePoint and Excel on iPad.