Compound Interest Calculator
Estimate future value from an initial deposit, monthly contributions, annual return, and compounding frequency.
Last updated: 2026-03-03
Compound interest calculator
Enter savings assumptions
Add your starting balance, monthly savings, expected return, and timeline.
Future Value
$44,665.27
Monthly compounding.
Total Principal
$29,000.00
Total Contributions
$24,000.00
Interest Earned
$15,665.27
Balance Composition
64.9% principal / 35.1% interest
Year-by-year breakdown
Track annual contributions, earned interest, and ending balance.
| Year | Starting Balance | Contributions | Interest Earned | Ending Balance |
|---|---|---|---|---|
| 1 | $5,000.00 | $2,400.00 | $439.97 | $7,839.97 |
| 2 | $7,839.97 | $2,400.00 | $645.27 | $10,885.24 |
| 3 | $10,885.24 | $2,400.00 | $865.41 | $14,150.65 |
| 4 | $14,150.65 | $2,400.00 | $1,101.47 | $17,652.12 |
| 5 | $17,652.12 | $2,400.00 | $1,354.59 | $21,406.71 |
| 6 | $21,406.71 | $2,400.00 | $1,626.01 | $25,432.72 |
| 7 | $25,432.72 | $2,400.00 | $1,917.05 | $29,749.77 |
| 8 | $29,749.77 | $2,400.00 | $2,229.13 | $34,378.90 |
| 9 | $34,378.90 | $2,400.00 | $2,563.77 | $39,342.67 |
| 10 | $39,342.67 | $2,400.00 | $2,922.60 | $44,665.27 |
Example scenarios
Apply realistic savings plans to see the impact of time and consistency.
Lump-Sum Investment
$10,000 one-time deposit at 7%
Shows how a single deposit compounds over 10 years with no ongoing contributions.
Result: $20,096.61 future value
Regular Savings
$1,000 start + $300/month at 4.5%
A common long-term savings setup with recurring monthly deposits.
Result: $21,395.46 future value
Long-Term Retirement
$5,000 start + $200/month at 7%
Highlights how time can drive growth over a 30-year horizon.
Result: $284,576.69 future value
How Compound Interest Works
Compound interest means your money earns returns on both your original deposits and the interest already accumulated. Over time, this creates a snowball effect: as your balance grows, each period's interest amount grows too.
Core formulas
FV_principal = P x (1 + r/n)^(n x t)
FV_contributions = PMT x [((1 + r/n)^(n x t) - 1) / (r/n)]
Where P is initial amount, PMT is monthly contribution, r is annual rate, n is compound periods per year, and t is years.
This calculator models monthly contributions added at the end of each month and supports daily, monthly, quarterly, or annual compounding. More frequent compounding can increase returns because earned interest gets reinvested sooner.
Time is the biggest lever. Consistent contributions over long horizons can produce much larger balances than short bursts of saving. Even if rates are uncertain, starting early gives compounding more periods to work in your favor.
Compound interest FAQs
Common questions about growth projections, assumptions, and interpretation.
What is the difference between compound interest and simple interest?
Simple interest is calculated only on your original principal, while compound interest is calculated on both principal and previously earned interest. Over long time horizons, compounding typically produces much larger balances.
How does compounding frequency affect returns?
More frequent compounding applies interest to your balance more often, which can increase your ending value. The difference is usually modest over short periods but can become meaningful over decades.
Does this calculator include inflation or taxes?
No. Results are nominal pre-tax estimates. Inflation, taxes, fees, and investment performance variability are not included, so real-world outcomes may differ.
What annual return should I use?
Use a conservative assumption based on your asset mix and risk tolerance. For planning, many people model multiple scenarios (for example 4%, 6%, and 8%) instead of relying on a single number.
Why is starting earlier so impactful?
Time gives compounding more cycles to work. Starting earlier can increase final value significantly, even when monthly contributions are modest, because growth compounds on prior growth for longer.
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Disclaimer
This calculator provides estimates for educational purposes only and is not financial advice. Actual returns vary by market performance, account fees, contribution timing, and taxes. Consult a qualified financial professional for personalized planning advice.