Monthly Investment Calculator
Explore the potential effect of regular contributions and compound growth. Results are illustrative, not guaranteed.
Your details
Your entries stay in your browser and are not submitted or stored. A share link stores the values in its URL.
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Projection
How the result changes over time
What-if scenario
A small monthly improvement
Milestones
Your projection checkpoints
A compact view of how the estimate develops. Values update with every input.
Calculator documentation
How to use the investment growth calculator
This section explains every input and interactive feature used in the calculator above.
Field-by-field guide
- Starting balance
- The amount already invested at the start.
- Monthly contribution
- The contribution made at the end of every month.
- Estimated annual return
- An illustrative gross annual return before the fee entered below.
- Investment period
- How long contributions and compounding continue.
- Annual fees
- Annual fund, advisory, or platform costs, modeled as a reduction in return.
- Expected inflation
- Expected annual price growth, used to translate the ending balance into today’s purchasing power.
- Annual contribution increase
- The percentage by which the monthly contribution rises after each completed year.
Calculation workflow
- 1Add the starting balance and monthly contribution.
- 2Use an expected return net of your risk expectations, then enter fees.
- 3Model annual contribution increases and compare future dollars with today’s purchasing power.
Planning tips
- ✓Small fee differences compound over long periods.
- ✓Increase contributions when income rises.
- ✓Treat projections as ranges, not promises.
Features and outputs
Live results
Every edit recalculates the headline and supporting metrics immediately.
Projection chart
Balance mode shows change over time; breakdown mode compares the components of the result.
What-if scenario
A calculator-specific improvement is modeled beside the current plan.
Milestone table
Selected checkpoints expose the projection behind the summary.
Share link
Copy share link encodes current inputs in the URL without sending them to a server.
Reset values
Restores all fields to the page defaults and clears shared URL values.
Frequently asked questions
Are returns guaranteed?+
No. The calculator applies a constant illustrative rate; real returns vary and losses are possible.
How are fees modeled?+
Annual fees reduce the entered annual return before monthly compounding.
What are today’s dollars?+
They discount the future balance by your inflation assumption to estimate future purchasing power.