Interest Rate Calculator
Last updated: November 5, 2026
Estimate a simple annual interest rate from principal, total interest and time.
Estimated annual simple interest rate
—
- Total return on principal: —
- Average interest per year: —
- Ending amount: —
On this page
Quick summary: Estimate a simple annual interest rate from principal, total interest and time.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate a simple annual interest rate from principal, total interest and time.
How to use it
Enter Principal amount ($); Total interest paid or earned ($); Time period (years). Select Calculate to update the results.
How the calculation works
For simple interest, annual rate equals total interest divided by principal and years.
Worked example: starting scenario
| Principal amount ($) | 10000 |
|---|---|
| Total interest paid or earned ($) | 1800 |
| Time period (years) | 3 |
| Estimated annual simple interest rate | 6% |
|---|---|
| Total return on principal | 18% |
| Average interest per year | $600.00 |
| Ending amount | $11,800.00 |
Important limitations
This does not solve an amortized loan APR or account for compounding, fees or changing balances.
Simple rate is different from compound yield
For $10,000 principal earning $1,800 over three years, the simple annual rate is 1,800 / (10,000 × 3) = 6%. A compound annual growth rate instead solves (11,800/10,000)^(1/3) − 1 and is about 5.67%. This form uses the simple-rate definition and does not reconstruct monthly loan APR or the effects of deposits and withdrawals.