Project a starting balance with compound interest, recurring deposits, recurring withdrawals, or both. See how payment timing and annual increases affect the balance, compare with a zero-interest scenario, and inspect monthly or yearly cash flows.
How to use this calculator
- Enter the amount you are starting with and the annual interest rate.
- Set the term in years and months, then choose how often interest compounds.
- Open Recurring deposits or Recurring withdrawals if money moves in or out regularly. Each has its own frequency and payment timing.
- Set an annual increase as a percentage of the previous year's payment or a fixed amount added to each payment. Leave the amount at zero to disable that cash flow.
- Read the balance, interest, and withdrawals paid. Choose a monthly schedule, or expand each yearly row to see its months.
Use Compare scenarios to keep a baseline, then change one assumption. Use the Investment Calculator if you need to solve for a target contribution, return, starting amount, or investment length.
Understanding your results
| Result | What it tells you |
|---|---|
| Ending balance | Starting amount + additional deposits + interest − withdrawals actually paid. |
| Total interest | Interest earned over the full term, including interest subsequently withdrawn. |
| Effective annual rate (APY) | The annual effect of the selected compounding frequency. It can differ from the nominal rate you enter. |
| Growth table | Deposits, withdrawals, interest, and the closing balance for each period. |
| Unfunded withdrawals | Requested withdrawals that available funds could not cover. |
To compare two scenarios, keep the starting deposit and term the same and change one assumption, such as the rate. Save each result if you want to return to it later.
Simple vs. compound interest
| $100 at 10% for 2 years | |
|---|---|
| Simple interest | $120 ($10 + $10) |
| Compound interest | $121 ($10, then $11) |
Examples
$10,000 · 5% · monthly · 10 years
A $10,000 deposit at 5% compounded monthly grows to about $16,470 after 10 years — roughly $6,470 of interest — at an effective annual rate of 5.116%.
10% compounded semiannually
A 10% nominal rate compounded twice a year produces an APY of 10.25%, so $1,000 becomes $1,102.50 after one year.
Monthly contributions and timing
At 12% nominal interest compounded monthly, an initial $1,000 plus $100 deposited at the end of each month grows to $2,395.08 after one year. Moving the same 12 deposits to the beginning of each month gives each deposit one extra month of growth, producing $2,407.76. Contributions total $2,200 in either case.
Formula
Compound interest grows the balance each period and then earns interest on that interest. For a starting amount P, annual rate r, n compounding periods per year, and t years:
A = P · (1 + r/n)^(n·t) (continuous: A = P · e^(r·t))
Effective annual rate (APY) = (1 + r/n)^n − 1
With cash flows, total interest = ending balance − initial amount − additional deposits + withdrawals paid. Each cash flow grows from its payment time using the same effective growth factor.
Assumptions and limits
The rate is constant and the model excludes taxes, fees, and inflation. All money inputs use the selected display currency; changing the currency does not exchange or rescale money. Worked examples here are in US dollars.
Cash-flow periods are evenly spaced: 12 monthly, 26 biweekly, 52 weekly, or 365 daily periods per year. They are not a dated bank schedule. Between cash flows the model uses fractional-period growth equivalent to the chosen compounding rate. Actual account crediting and day-count rules may differ.
Beginning payments start immediately; end payments occur after a complete payment period. A partial final period receives no extra end payment. At a period boundary, the previous period closes before the next begins. Within either step, deposits are applied before withdrawals. The schedule includes opening payments in its first row, and the graph shows the balance after opening payments at time zero.
Annual increases begin with the second year's payments. Percentage increases compound; fixed increases add the same amount to each recurring payment every year. A zero recurring amount remains disabled even if an increase is entered.
Withdrawals cannot make the balance negative. Any unfunded amount is reported as a shortfall and is not deferred or treated as borrowing. The zero-interest comparison uses the same requested cash flows, but may pay fewer withdrawals if it runs out sooner; compare both Withdrawals paid and Unfunded withdrawals, not ending balances alone. The contribution/interest donut describes all money contributed and earned during the term, including amounts later withdrawn.
APY describes the annual effect of compounding, not a guaranteed account yield. The SEC compound-interest explanation provides a reference for the core growth relationship.
Compounding a sequence of trading gains and losses
A nominal annual savings rate is different from a return per trade or per month. A gain followed by an equally sized percentage loss does not restore the starting balance. Use the forex compounding calculator to enter gains and losses in order, separate new contributions from profits, and model withdrawing part of positive gains.
Daily dates and scheduled savings
For calendar dates, selected earning weekdays, withdrawals and partial reinvestment, use the Daily Compound Interest Calculator. For regular investing with annual contribution increases, try the SIP Calculator. To solve a contribution or time needed for a target, use the Savings Goal Calculator. Each page explains its timing and return assumptions.