Interest that accrues only on the original principal.
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 |
|---|---|---|
| Principal | $ | Enter a numeric value. |
| Annual rate | % | Enter a numeric value. |
| Time | yrs | Enter a numeric value. |
Formula
The calculation is based on the following relationship:
I = P · r · t
Worked example
Using the default values loaded into the calculator above, the result is:
| Input | Value |
|---|---|
| Principal ($) | 10000 |
| Annual rate (%) | 5 |
| Time (yrs) | 3 |
| Output | Value |
|---|---|
| Interest | $1,500.00 |
| Total amount | $11,500.00 |
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 Simple Interest Calculator do?
Interest that accrues only on the original principal.
What result do the default values produce?
With the values pre-loaded in the calculator, interest comes to $1,500.00.
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.
What formula does the Simple Interest Calculator use?
I = P · r · t
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.