Compound Interest Goal Plan Worksheet
Enter a goal, a time horizon, and a return assumption to see exactly how much you need to save each month — with milestone balances and printable output.
Your Plan Inputs
Typical planning range is 4%–8%. Returns are assumptions, not guarantees.
Results
Monthly Deposit Needed
$1,011
1,011 per period with Monthly (12x / year)
Principal Only (Total Contributions)
$252,523
What you deposit yourself
Target Amount
$500,000
Your total goal
Growth Needed to Bridge the Gap
$247,477
Return on your deposits
Milestone Balances
| End of Year | Projected Balance | Contributions | Growth |
|---|---|---|---|
| Year 1 | $23,082 | $22,126 | $956 |
| Year 5 | $83,992 | $70,631 | $13,361 |
| Year 10 | $183,796 | $131,261 | $52,535 |
| Year 15 | $318,417 | $191,892 | $126,525 |
| Year 20 | $500,000 | $252,523 | $247,477 |
Scenario Comparison
How the required monthly deposit changes across three assumed annual returns. All three are illustrative — actual market returns vary and are not guaranteed.
| Scenario | Assumed Annual Return | Monthly Deposit Needed | Growth Supplied |
|---|---|---|---|
| Conservative | 4% | $1,303 | $177,367 |
| Neutral(your input) | 6% | $1,011 | $247,477 |
| Optimistic | 8% | $765 | $306,346 |
How This Worksheet Works
The worksheet solves the future-value of an annuity formula for the payment. With a per-period rate r = annual return ÷ compounding periods per year and n = years × periods per year, the formula is:
FV = PV(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)]
Rearranged, the required per-period contribution is PMT = (FV − PV(1+r/n)^(nt)) × (r/n) / ((1+r/n)^(nt) − 1). The monthly-equivalent deposit is then scaled from the per-period amount. The milestone table applies the same compounding to years 1, 5, 10, 15, and 20, and the scenario table re-solves the formula at 4%, 6%, and 8% assumed returns so you can see how sensitive your plan is to the return assumption.
* The return rates used here are planning assumptions or user inputs, not promises of performance. Actual results depend on market conditions, fees, taxes, and inflation.
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Frequently Asked Questions
How much do I need to save each month to reach my goal?
The worksheet solves the future-value of an annuity formula for the monthly payment: FV = PV(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)]. It returns the monthly-equivalent deposit that, combined with your starting amount and assumed annual return, reaches your target on schedule. For example, $1,000,000 in 20 years at a 6% assumed return starting with $10,000 requires roughly $2,093 per month.
Does the compounding frequency affect how much I need to save?
Yes, but the effect is usually small. More frequent compounding (monthly vs quarterly vs yearly) means interest is added to your balance more often, so the required deposit is slightly lower at the same annual rate. Monthly compounding is the most common default for savings plans.
What return rate should I assume?
CompoundFig does not promise any return. A 4%–8% planning range is commonly used for illustrations: 4% is a conservative assumption, 6% a neutral one, and 8% an optimistic one. Historical US stock-market averages are higher in nominal terms, but actual results vary by asset class, fees, taxes, and market timing. Use a conservative number and revisit your plan regularly.
How long will it take to reach my target amount?
The time depends on your monthly deposit, starting balance, and assumed return. The milestone table shows projected balances at the end of years 1, 5, 10, 15, and 20 (bounded by your horizon). Increasing the monthly deposit, adding a starting amount, or extending the timeline each shortens the gap to your goal.
How do I print this worksheet?
Click the "Print Worksheet (Letter)" button and your browser will open the print dialog formatted for Letter-size paper. The printable output includes your inputs, the required monthly deposit, the milestone table, and the scenario comparison, along with a compliance note.