Grow a starting balance with regular contributions and compounding interest.
How to use this calculator
Every field updates the result as you type — there is no submit step. The inputs below are pre-filled with a realistic example so you can see how the tool behaves before entering your own figures.
| Field | Unit | What it means |
|---|---|---|
| Starting amount | $ | Enter a numeric value. |
| Regular contribution | $ | Enter a numeric value. |
| Contribution frequency | — | Choose one of the available options. |
| Annual interest rate | % | Enter a numeric value. |
| Compounding | — | Choose one of the available options. |
| Years | yrs | Enter a numeric value. |
| Tax rate on interest | % | Enter a numeric value. |
Worked example
Using the default values loaded into the calculator above, the result is:
| Input | Value |
|---|---|
| Starting amount ($) | 10000 |
| Regular contribution ($) | 200 |
| Contribution frequency | Monthly |
| Annual interest rate (%) | 5 |
| Compounding | Monthly |
| Years (yrs) | 10 |
| Tax rate on interest (%) | 0 |
| Output | Value |
|---|---|
| Ending balance | $47,526.55 |
| Starting amount | $10,000.00 |
| Total contributions | $24,000.00 |
| Total interest earned | $13,526.55 |
| Effective annual rate | 5.1162% |
Reading the result
Financial projections compound small assumption changes into large differences over time. Rates, fees and tax treatment vary by lender and jurisdiction, so treat the output as a well-structured estimate for comparing options rather than a quotation.
Figures that change annually — tax bands, contribution limits, statutory rates — are exposed as editable inputs. Check them against current published values before relying on the result.
Sharing and saving a calculation
The "Copy link" button encodes every value you have entered into the page URL. Opening that link restores the calculation exactly, which makes it easy to bookmark a scenario, send it to someone else, or keep several variations side by side in separate tabs.
Frequently asked questions
What does the Interest Calculator do?
Grow a starting balance with regular contributions and compounding interest.
What result do the default values produce?
With the values pre-loaded in the calculator, ending balance comes to $47,526.55.
Is this calculator free to use?
Yes. It is free, requires no account, and runs entirely in your browser — nothing you enter is transmitted or stored on a server.
Can I save or share a calculation?
Yes. The "Copy link" button builds a URL containing all your entered values. Anyone opening that link sees the same calculation.
How accurate is the result?
The calculation itself is exact for the inputs given. Real-world accuracy depends on how well those inputs reflect your actual situation, so review the assumptions before relying on the figure.