Currency: USD
Enter all amounts in USD. Changing currency keeps numbers unchanged; no exchange rate is applied.
- Interest
- $487,500.00
- Final amount
- $737,500.00
How it works
Convert the duration only once
For 1,000 at a 6% annual simple rate over three months, interest is 15. Choose months and enter 3, while keeping the rate at 6%; dividing the rate by twelve again would understate interest.
When simple interest is the right model
Simple interest uses the original principal for the entered time period, without adding earlier interest to the base. Match the time units to the rate before interpreting the result. The missing-quantity mode can solve for an unknown input when the other values are known. Do not use a simple-interest result as a substitute for a loan schedule that compounds or reduces principal through payments.
Simple interest: formula and assumptions
Interest = principal×annual rate×years.
The interest base remains the original principal throughout the term. Monthly durations are normalized by dividing by 12; the annual rate remains unchanged.
Solve a missing quantity: formula and assumptions
Balance=principal×(1+rate×time).
Interest is not compounded; rates use a yearly basis. Monthly durations are normalized by dividing by 12; the annual rate remains unchanged.
Worked example
Reference example currency: USD. These fixed examples do not change with your calculator preferences.
Using the Simple interest example:
- Loan amount ($)
- 250000
- Annual interest rate (%)
- 6.5
- Duration (years)
- 30
- Duration unit
- Years
Interest = principal×annual rate×years.
Example result
Interest: $487,500.00
Final amount: $737,500.00
These are illustrative inputs. Change the values to explore a different scenario.
Formula references
- CFPB: understanding mortgages (opens in a new tab)
- Investor.gov: financial tools and calculators (opens in a new tab)
References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.
Common questions
How does simple interest differ from compound interest?
Simple interest is calculated only on the original principal. Compound interest also earns interest on previously accumulated interest.
What time unit should I use with the annual rate?
Use years, including a fractional year when appropriate. The inverse model also treats the rate as an annual rate.
Prepared by Finflo. See our methodology and editorial policy. Read the relevant professional-advice limitations.