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Investment Goal Calculator

This calculator answers the two questions behind every savings plan: how much do I need to invest each month to reach a target, and what will a given monthly amount grow into? Both come from the future-value-of-an-annuity formula. For a goal, PMT = FV × r ÷ ((1 + r)ⁿ − 1); for a projection, FV = PMT × ((1 + r)ⁿ − 1) ÷ r, where r is the monthly rate (annual return ÷ 12) and n the number of monthly contributions. Assumptions: contributions land at the end of each month (an ordinary annuity), returns compound monthly at a constant rate, and results ignore taxes, fund fees, and inflation — real markets deliver lumpy returns around the average, so treat the output as a planning baseline, not a promise. The expected-return input is yours to choose; the FAQ covers what is realistic.

Required monthly contribution

$820

invested at the end of each month for 360 months at 7% a year (compounded monthly)

Total contributed

$295,089

Investment growth

$704,911

Final value

$1,000,000

Year-by-year growth
YearContributed so farPortfolio value
1$9,836$10,158
2$19,673$21,051
3$29,509$32,730
4$39,345$45,255
5$49,181$58,684
6$59,018$73,084
7$68,854$88,526
8$78,690$105,083
9$88,527$122,838
10$98,363$141,876
11$108,199$162,291
12$118,036$184,181
13$127,872$207,653
14$137,708$232,822
15$147,544$259,811
16$157,381$288,751
17$167,217$319,783
18$177,053$353,058
19$186,890$388,739
20$196,726$426,999
21$206,562$468,025
22$216,399$512,017
23$226,235$559,189
24$236,071$609,771
25$245,907$664,009
26$255,744$722,168
27$265,580$784,532
28$275,416$851,404
29$285,253$923,110
30$295,089$1,000,000

How to use the investment goal calculator

  1. Pick a mode: find the monthly amount for a goal, or project what a monthly contribution grows into.
  2. Enter the target (or monthly amount), your time horizon in years, and an expected annual return — 6–8% is a common long-run planning range for diversified stock portfolios.
  3. Read the headline number plus total contributed and investment growth.
  4. Expand the year-by-year table to see how growth accelerates: in later years the portfolio earns more from compounding than from your deposits.

Why the return assumption dominates everything

Hold the contribution fixed at $820/month for 30 years and vary only the return: at 5% you end near $682,000, at 7% near $1,000,000, and at 10% near $1,850,000. A two-point change in the assumption swings the outcome by more than the entire amount you contribute. That is why this page nags when you enter a return above 12% — an aggressive assumption does not make money grow faster, it just makes the plan quietly underfunded. The professional habit is to plan on a conservative number and let upside shorten the timeline rather than betting the goal on it.

Monthly amount needed for $100,000, by horizon and return

Horizon5%7%9%
10 years$644$578$517
20 years$243$192$150
30 years$120$82$55

Each cell is PMT = 100,000·r/((1+r)ⁿ − 1) with monthly compounding, rounded to the dollar. Read it vertically and the lesson is time: at 7%, starting 10 years earlier cuts the required amount from $578 to $192 — a third of the effort for the same goal. No realistic improvement in returns matches the power of starting earlier.

Fitting the plan into a real budget

A monthly investment plan only survives if it fits your cash flow after taxes and fixed costs. Start from take-home pay, not gross — the take-home pay calculator shows the number that actually hits your account — and treat the contribution like a bill you pay first. Fees matter too: a fund charging 1% more per year than an index alternative consumes roughly $100,000 of the $1M-in-30-years example, because the fee compounds against you with the same arithmetic that grows the portfolio. If part of your surplus is competing with a loan, compare the loan's APR against your assumed return with the loan prepayment calculator before defaulting to the market.

Frequently asked questions

How is the required monthly amount calculated?

PMT = FV·r / ((1+r)^n − 1), the ordinary-annuity formula solved for the payment. Example: $1,000,000 in 30 years at 7% a year. r = 0.07/12 = 0.005833, n = 360, (1.005833)^360 ≈ 8.116, so PMT = 1,000,000 × 0.005833 ÷ 7.116 ≈ $820 per month. You would contribute about $295,100 over 30 years; the remaining ~$704,900 is compound growth. Shorter example: $50,000 in 10 years at 6% needs about $305/month.

What is a realistic expected return?

Long-run US stock-market returns have historically averaged in the high single digits to around 10% per year before inflation, but that average hides decade-long stretches well above and below it. Most planners model diversified stock-heavy portfolios at 6–8% nominal, bond-heavy mixes lower. Entering 12%+ makes any goal look easy and is the most common way these plans fail. A sound habit: run the plan at 5%, 7%, and 9% and make sure the 5% case is still acceptable.

How badly does inflation distort the result?

Significantly over long horizons. At 3% inflation, $1,000,000 received 30 years from now buys what about $412,000 buys today (1,000,000 ÷ 1.03^30). Two clean fixes: either inflate your target (a $1M goal in today's dollars becomes roughly $2.43M in 30 years at 3%), or use a real return — your expected return minus expected inflation, e.g. 7% − 3% = 4% — and read the result directly in today's dollars.

Why does the order of mode matter — $500/month vs a $500k goal?

They are the same equation read in opposite directions. $500/month for 20 years at 7% grows to about $260,500 — of which only $120,000 is your money; $140,500 is growth. Inverting: hitting exactly $260,500 in 20 years at 7% requires exactly $500/month. The projection mode is useful when your budget is fixed; the goal mode when the target (a down payment, college, retirement number) is fixed.

Does it matter that contributions are monthly instead of yearly?

Yes, slightly in your favor. Twelve monthly contributions of $500 beat one year-end contribution of $6,000 because earlier dollars compound longer. The model here assumes end-of-month contributions; contributing at the start of each month (an annuity due) multiplies the future value by one extra month of growth, (1 + r) — about 0.6% more at a 7% annual return. Real-world timing differences are far smaller than the error in any return assumption.

Should I invest monthly or pay down debt first?

Compare interest rates to expected returns. Paying off a credit card charging 22% APR is a guaranteed, tax-free 22% return — no diversified portfolio reliably beats that. Most planners suggest clearing high-interest debt and securing any employer 401(k) match (an instant 50–100% return on matched dollars) before funding taxable monthly investing. Low-rate debt like a 3% mortgage is the usual exception, since expected market returns exceed the rate.

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