Investment Goal Calculator

Investment Goal Calculator

Have a number in mind? Enter your goal, how long you have, and an expected return to find the monthly investment that gets you there — or the single lump sum you could invest today instead. See how much is your own money and how much is market growth. Works in any currency.

The future amount you want to have — in any currency.

Presets are illustrative examples only, not a guaranteed return.

Money you already have or have invested toward this goal.

Working backward from a number instead of forward from a habit

Most savings tools start with what you can set aside and project where that habit leads. This one runs the opposite direction: you already know the number you need — a wedding, a down payment, a retirement balance, a child's tuition fund — and it solves for the monthly deposit that closes the gap between where you are and where you need to be, by your deadline. That reverse framing turns a vague intention ("save what's left over") into a fixed, checkable monthly number the moment a goal acquires both a date and a price tag.

Reading the five inputs

  1. Target amount — the balance you want on the horizon's last day, in whatever currency you're planning in. Nominal, not adjusted for anything.
  2. Time horizon — whole years from today to the goal date. Round down if you're between years; a shorter horizon asks for a larger, safer monthly figure rather than an optimistic one.
  3. Expected annual return — the growth rate you're assuming, before fees. The input most likely to be wrong in hindsight, so treat it as a planning assumption, not a promise.
  4. Starting amount — money already set aside toward this goal. Zero just means the whole target has to come from future contributions plus growth.
  5. Annual inflation — optional, and it changes only the "goal in today's money" figure, not the required monthly investment. Use it to see what your nominal target is really worth once time erodes it.

How the monthly figure is actually solved

The calculation happens in two stages. First, any starting amount is carried forward on its own, compounding monthly for the full horizon. Second, whatever the target is still missing after that is treated as a debt your monthly contributions must retire, with each contribution assumed to land at the start of its month (so it earns that month's growth too, unlike an ordinary end-of-month annuity). Dividing the remaining gap by a growth factor built from the monthly rate and the number of months gives the required contribution.

In plain terms: monthly investment = (target − starting balance grown to the goal date) ÷ (a factor measuring how much one unit invested every month, starting immediately, grows to by the deadline). A higher return or a longer horizon makes that factor larger — which is why both push the required monthly number down, sometimes dramatically.

Three worked examples across different horizons

Short horizon, low return — an 18-month wedding fund. Target 15,000, horizon 1.5 years (18 months), expected return 2% (a cautious, near-cash assumption), no starting balance. The required contribution comes out to about 820 a month. Total contributions over 18 months are roughly 14,764 — growth contributes only about 236, under 2% of the goal. Short, low-return goals are funded almost entirely by your own deposits.
Medium horizon — a 50,000 down payment in 5 years. Same zero starting balance, but a 5-year horizon and a 5% expected return. The required monthly investment drops to about 732. Contributions over 60 months total roughly 43,931, so growth supplies about 6,069 — close to 12% of the goal.
Long horizon with a head start — a 1,000,000 retirement goal in 30 years. Starting balance 20,000, expected return 8%. That starting balance alone grows roughly eleven-fold by the deadline, so the required monthly contribution is only about 521 — a fraction of the ≈2,778 a naive "target ÷ months" calculation would suggest. Total contributions end up near 207,470, so growth supplies close to 793,000, about 79% of the entire goal — the clearest illustration of why starting early changes the math this much.

Reference: monthly investment needed per 10,000 of target

To compare horizons and return assumptions at a glance, here is the required monthly contribution per 10,000 of target, with no starting balance — scale it to your own goal by multiplying (e.g. a 250,000 goal needs 25× the figure below).

Horizon4% return7% return10% return
5 years150.33138.87128.07
10 years67.6957.4448.41
20 years27.1719.0913.06
30 years14.368.154.39

Notice how much more the return assumption matters at 30 years than at 5: at 5 years, moving from 4% to 10% trims the monthly figure by about 15%; at 30 years, the same jump cuts it by roughly 70%. Return assumptions matter most on the longest horizons — which is also where they're hardest to verify in advance.

Common mistakes and practical tips

What this projection does not cover

The math here is arithmetic compounding at a single, constant assumed rate — it cannot know how a real portfolio's returns will actually be sequenced year to year, and a market downturn late in the horizon has a very different effect than the same downturn early on ("sequence of returns" risk), even if the long-run average ends up identical. The tool also does not model taxes on investment gains, account contribution limits, or irregular windfalls such as bonuses — for those, treat a lump sum contribution as reducing the goal that still needs to be funded monthly, then recalculate. None of this is investment, tax, or financial advice; it is a transparent arithmetic projection meant to make a savings target concrete enough to check your progress against.

Sources & further reading

Frequently asked questions

What formula tells me the required monthly investment?

This investment goal calculator works backwards from your target. It first grows any starting amount forward — starting × growth, where growth = (1 + monthly rate) raised to the number of months. Whatever the goal is still short of is funded by your monthly contributions, invested at the start of each month (an annuity-due). The required monthly investment is (target − starting × growth) ÷ the annuity-due factor, where the factor = (1 + m) × (growth − 1) ÷ m and m is your annual return divided by 12. Worked example: to reach 100,000 in 20 years at 7%, growth ≈ 4.04, the factor ≈ 524, so with no starting amount you need about 191 a month. The tool rounds this figure up so a small rounding gap never leaves you short of the goal.

Should I invest monthly or a single lump sum today?

There are two ways to reach the same goal, and this savings goal calculator shows both. The required monthly investment spreads the cost across every month until your deadline. The lump sum today is the single amount you could invest right now instead, computed as target ÷ growth minus any starting amount — because that one deposit has the full horizon to compound. The lump sum is almost always far smaller than the sum of all the monthly contributions, since it starts working immediately, but it requires the cash up front. Monthly investing (dollar-cost averaging) is what most people actually do because it matches a salary; the lump sum is the benchmark for money you already have sitting idle.

Why are the 4%, 7% and 10% return presets illustrative only?

The expected return is an assumption you choose, not a rate anyone can promise. The presets are round reference points often cited for broad index funds — for example the S&P 500 has averaged roughly 7% a year after inflation and around 10% before inflation over long history, while 4% is a more cautious figure. Real markets do not deliver a smooth annual number: some years are strongly positive, others negative, and past averages never guarantee the future. A higher assumed return lowers the monthly investment the tool asks for, so it is tempting to be optimistic — but that also makes the plan more fragile. To stress-test a goal, run it again with a lower return and see how much more you would need to invest each month.

How much of my goal comes from my money versus market growth?

The tool splits your goal into two parts. Total contributions is what you actually pay in — your starting amount plus every required monthly investment. Market growth is the rest of the goal, the compounding that lands on top of your money. The highlighted line — market growth covers X% of your goal — shows that split for your exact inputs. Over short horizons your own contributions do nearly all the work; over twenty, thirty or more years, market growth often becomes the larger slice, which is why starting early lets a smaller monthly amount reach the same target. Because the calculator makes market growth cover part of the goal, the monthly figure it asks for is smaller than simply dividing the target by the number of months.

How do I adjust my goal for inflation?

A target set in today's terms will not buy the same thing decades from now, because inflation erodes purchasing power. Enter an annual inflation rate and this goal calculator shows your goal in today's money — the target divided by (1 + inflation) for each year of the horizon — so you can see what that future number is really worth now. If your goal is a real-world cost such as a house deposit or a child's education that itself rises with inflation, consider setting the target higher, or treat the today's-money figure as the honest yardstick. Leave inflation at 0 to work purely in nominal amounts. The required monthly investment is always calculated against the nominal target you enter.