Investment growth: what time and regular saving can do

What the calculator does

Enter the amount invested today, what you plan to add each month, an assumed annual return, and a time horizon. You can also choose how many years you will keep adding money. The projection continues after those contributions stop.

The graph separates the money you put in from the projected account value. The gap is modeled growth. Monthly and yearly schedules let you inspect the numbers or download them as CSV files.

The philosophy: a habit has a timeline

A monthly contribution is easy to see in your budget. Its possible effect decades later is harder to picture. This tool connects the two without asking you to build a spreadsheet.

It also separates stopping saving from spending the money. Reaching the contribution-stop marker means new deposits end; it does not mean the account is withdrawn. That distinction lets you explore saving intensively for a period and leaving the balance invested afterward.

Try a zero-return baseline

Start with $10,000, add $500 a month for 10 years, and set the horizon to 30 years. At 0% return, the ending value is $70,000: your starting $10,000 plus $60,000 of contributions. It stays flat after year 10 because neither growth nor further deposits adds anything.

Now enter a positive return assumption. Watch the account continue growing after the saving-stop marker, while the contributed-money line stays flat. Then compare saving for 10 years with saving for 20, keeping everything else unchanged.

How to read the curve

The annual return is converted to an equivalent monthly rate. Each month, the existing balance grows first and the contribution is added afterward. At zero return, contributions create a straight rising line; when both return and contributions are zero, the line stays flat.

A smooth rising curve describes the assumption you entered. Actual investments can lose value and do not deliver the same return every month. This calculator leaves out taxes, fees, inflation, withdrawals, and market variability.

Where to go next

If you want to connect accumulation with retirement withdrawals, use the Retirement Planner guide. If your question is when you could stop contributing and still work toward a later retirement, read about Coast FIRE.