How it works
Compute simple and compound interest with regular monthly contributions.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
5-
?principal=Principal AmountNumber · Optional · Default: 10,000
-
?rate=Annual Interest RateNumber · Optional · Default: 5
-
?time=Time Period (Years)Number · Optional · Default: 10
-
?contribution=Monthly ContributionNumber · Optional · Default: 0
-
?compoundFreq=Compounding FrequencyText · Optional · Default: 12
Outputs
1-
resultResultText · Primary output
result contains the calculator’s complete rendered result area, including its visible result cards, tables, charts, and messages.
Compute simple and compound interest growth
Description
The Interest Calculator allows you to project the growth of your savings or investments over time. It supports both simple and compound interest calculations and lets you include regular monthly contributions to see the power of consistent saving.
Inputs
- Principal Amount: The initial amount of money deposited ($).
- Annual Interest Rate: The annual return rate (%).
- Time Period: The duration of the investment in years.
- Monthly Contribution: Additional amount added each month ($).
- Compounding Frequency: How often interest is compounded (Monthly, Quarterly, Annually).
Outputs
- Final Balance: The total value of the investment at the end of the term.
- Total Interest: The total amount of interest earned.
Chart
- Growth Chart: A line/area chart showing the growth of “Balance” vs. “Principal Invested” over time.
“Good to Know”
- Compound interest allows your interest to earn interest, accelerating growth over long periods.
- More frequent compounding (e.g., Monthly vs Annually) typically results in higher returns.
- Regular contributions, even small ones, can significantly boost your final balance through dollar-cost averaging and compounding.
Examples
Example 1: High Yield Savings
- Input:
- Principal: $10,000
- Rate: 4.5%
- Time: 5 Years
- Contribution: $200
- Frequency: Monthly
- Output:
- Final Balance: ~$25,540
- Total Interest: ~$3,540
Example 2: Long Term Investment
- Input:
- Principal: $5,000
- Rate: 7%
- Time: 20 Years
- Contribution: $100
- Frequency: Annually
- Output:
- Final Balance: ~$69,300
- Total Interest: ~$40,300
Example 3: Short Term CD
- Input:
- Principal: $50,000
- Rate: 5%
- Time: 1 Year
- Contribution: $0
- Frequency: Monthly
- Output:
- Final Balance: ~$52,558
- Total Interest: ~$2,558