More in Long Horizon
What this calculator does
This calculator shows the real cost of delaying investments. Time in the market is usually the biggest driver of wealth.
The math
Future value = monthly contribution × (((1 + monthly rate)^months − 1) ÷ monthly rate). The difference = later-start value − now-start value.
Worked example
Investing $300 per month starting at age 25 versus age 35 at 7% annual return can mean a difference of over $200,000 by retirement.
Why this matters
Small decisions compound over decades. This calculator shows the long-term price of waiting or choosing the wrong path.
Methodology and transparency
This page publishes the exact formula used to compute the result, so you can verify it in a spreadsheet or check the assumptions against your own situation. The worked example uses the tool default inputs; change any number and the result updates live in your browser. No data is sent or stored.
Common questions
Why does starting early matter so much?
Compound interest means early contributions earn returns for longer, and those returns also earn returns.
What if I start late?
You may need to contribute more per month to catch up. The calculator shows exactly how much.
Is 7% a realistic return?
It is a common long-term average for a diversified stock portfolio, but actual returns vary.