Compound Interest Calculator with Monthly Contributions
Estimate future value from a starting balance, monthly contributions, annual rate, compounding frequency, contribution timing, and time horizon. Use it to compare savings growth and investment growth scenarios before moving numbers into a spreadsheet.
Try a common compound plan
Future value
$84,975
Total contributed
$50,000
Estimated interest
$34,975
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| 1 | $8,000 | $392 | $8,392 |
| 2 | $11,000 | $994 | $11,994 |
| 3 | $14,000 | $1,817 | $15,817 |
| 4 | $17,000 | $2,877 | $19,877 |
| 5 | $20,000 | $4,187 | $24,187 |
| 6 | $23,000 | $5,762 | $28,762 |
| 7 | $26,000 | $7,620 | $33,620 |
| 8 | $29,000 | $9,778 | $38,778 |
| 9 | $32,000 | $12,253 | $44,253 |
| 10 | $35,000 | $15,067 | $50,067 |
| 11 | $38,000 | $18,239 | $56,239 |
| 12 | $41,000 | $21,791 | $62,791 |
| 13 | $44,000 | $25,748 | $69,748 |
| 14 | $47,000 | $30,134 | $77,134 |
| 15 | $50,000 | $34,975 | $84,975 |
Principal
The starting balance that begins the projection.
Monthly contributions
Recurring deposits that can become a major driver of long-term future value.
Compounding
The schedule that determines how often interest is applied to the balance.
Starting balance
Use the amount already saved or invested before the projection starts.
Contribution timing
Choose start-of-month or end-of-month deposits to match how money is actually added.
Rate assumption
Use a realistic annual rate and remember the result excludes taxes, fees, inflation, and volatility.
monthly rate = (1 + annual rate / n)^(n / 12) - 1
The calculator converts the selected compounding frequency into an effective monthly rate, then simulates month-by-month growth and contributions.
Example: A $5,000 starting balance plus $300 per month at 6% for 10 years shows total contributions, estimated interest, and projected future value.
The result is an educational mathematical projection, not financial advice or a promise. Real savings rates and investment returns can change, and this page does not include taxes, inflation, account fees, or market volatility.
Calculations are handled in the browser for this tool based on the current public implementation. Avoid entering sensitive personal financial details unless you have reviewed the implementation.
Savings goal planning
Estimate how a starting balance and monthly deposits could grow toward a future savings target.
Monthly contribution scenarios
Compare different recurring contribution amounts and contribution timing assumptions.
Compounding frequency checks
Compare annual, quarterly, monthly, and daily compounding under the same annual rate.
Educational growth examples
Show how principal, contributions, interest, and time interact in long-term projections.
Compound interest with monthly contributions
Estimate future value from principal, recurring deposits, rate, and time horizon.
Savings growth calculator
Project a before-tax savings balance with simple rate and contribution assumptions.
Investment growth calculator
Compare long-term growth scenarios while keeping volatility, taxes, and fees separate.
Future value calculator
Check the projected balance for a selected annual rate and compounding schedule.
Example
A $5,000 starting balance plus $300 per month at 6% for 10 years shows how much growth comes from contributions versus interest.
Assumption
The rate is treated as a steady annual rate and converted into the selected compounding schedule before monthly simulation.
Limitation
Taxes, inflation, account fees, variable rates, and market volatility are not included.
Treating the rate as guaranteed
A steady annual rate is only an assumption. Savings rates, investment returns, fees, and inflation can change.
Mixing contribution timing
Start-of-month and end-of-month contributions produce different projections. Use the timing that matches the real deposit schedule.
Comparing after-tax and before-tax scenarios
This page does not model taxes. Compare scenarios on the same before-tax basis unless you have a separate tax estimate.
What is a compound interest calculator with monthly contributions?
It estimates future value from a starting balance, recurring monthly deposits, annual rate, compounding frequency, and time horizon.
What is compound interest?
Compound interest means interest earns interest. Over time, growth can accelerate because each period starts from a larger balance.
Why do monthly contributions matter?
Recurring contributions can become the main driver of long-term balance, especially when the starting principal is small.
Is daily compounding always better?
With the same annual rate, more frequent compounding is slightly higher, but the difference is often modest compared with contribution size and time horizon.
Can this be used for savings accounts?
Yes, for a rough before-tax savings estimate if you enter the account's annual percentage yield or expected rate.
Does the projection include inflation or taxes?
No. The projection is before tax and does not adjust for inflation, account fees, variable rates, or market volatility.
Suggested workflow
Long-term planning path
Move from savings growth to recurring investing and debt scenarios when comparing money decisions.