Interest by Days Calculator
Interest between two dates with 30/360, act/365, act/360 or act/act.
Runs entirely in your browser. Nothing is sent anywhere.
How it works
- 1Enter your values.
- 2See the result update instantly as you type.
- 3Change any value to compare scenarios.
About this tool
Interest by Days Calculator: Interest between two dates with 30/360, act/365, act/360 or act/act. Type your numbers and the result is calculated instantly — no button to press, nothing to install. All math runs locally in your browser, so the values you enter are never sent anywhere.
Example
| Input | |
|---|---|
| Starting amount | 10,000 |
| Interest rate (% per year) | 3.5 |
| Start date | 2026-01-15 |
| End date | 2026-07-31 |
| Day count convention | act/365 |
| Result | |
| Interest | 188.90 |
| Interest days | 197 |
| Year fraction | 0.539726 |
| Final amount | 10,188.90 |
How do I use the Interest by Days Calculator?
Enter your values. See the result update instantly as you type. Change any value to compare scenarios.
Is the Interest by Days Calculator free?
Yes. It is completely free with no sign-up, no usage limits and no watermark.
Is my data sent to a server?
No. Everything is calculated locally in your browser. Nothing you enter is uploaded, logged or stored.
Does it work on my phone?
Yes. It works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux — no app needed.