Savings Growth with Compound Interest

Live result on the frontend

The Savings Growth calculator is powered by a real Excel workbook. Calc Builder writes the visitor’s numbers into the sheet, lets the workbook recalculate and reads the results back to draw a dashboard and a year-by-year chart.

What it calculates

A visitor enters a starting deposit, a monthly contribution, an expected annual return and a number of years. The workbook returns:

• Final balance — the future value of the deposit plus every monthly contribution, compounded monthly.
• Total contributed — everything the visitor puts in over the period.
• Interest earned — the growth on top of the contributions, and its share of the final balance.
• Yearly table — contributions, interest and balance for every year, which the PHP code turns into a stacked bar chart.

How it’s built

The Spreadsheet screen holds the workbook and four input mappings (each Number field to a cell such as B3) and three output mappings (result cells back into PHP variables). The execution mode is custom, so the //[EXCEL] marker in the PHP Code shows exactly where the sheet runs.

After the marker $objPHPExcel is the loaded workbook, so the PHP Code also reads the yearly table (rows 14–53) to build the chart. The workbook is available for download below: import the calculator, then upload the Excel file on its Spreadsheet screen.

The input form as your visitors see it, styled with the Form Layout.

The Spreadsheet screen: the workbook is uploaded here and the execution mode is set.

Input mapping: each Calc Builder variable is written into a cell of the workbook before it recalculates.

The PHP Code: the //[EXCEL] marker runs the sheet, then the yearly table is read back to draw the chart.