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Investment Calculator

Investment Growth Calculator

What do you want to figure out?

$
$
%
Not sure? Tap a long-run yearly average (editable, not a promise):
Which one do I pick?
Match it to where your rate came from. Quoted averages like “the S&P returns about 10% a year” are figured yearly, so yearly is the honest match; that's the default here. A savings account or CD usually states a rate that adds monthly or daily; use that if you're matching a real account. More often = a slightly higher result. Your contributions still go in on their own schedule; this only sets how often growth is added.
%

Used to translate the future balance into today's buying power (real return = (1+return)÷(1+inflation) − 1). Set to 0 to ignore.

%
years

Money you add goes in at the end of each month and starts growing from there.

You'll have
Growth over time
Compare two options

Change one thing between A and B. Everything else stays the same, so you see exactly what that one change does.

Option A
%
Option B
%
What you started with$0
What you added over time$0
Growth on top$0
What it's really worth

Future dollars buy less than today's. Here's the same result in today's money, and what any yearly fee quietly costs.

Ending balance (future dollars)$0
In today's buying power$0
Lost to inflation$0
Range of outcomes (Monte Carlo)

Markets don't return a smooth number every year; good years and bad ones stack up differently. We run 500 randomized paths around your return and show the honest spread instead of a single tidy line.

Average yearly return
%
Ups & downs (volatility)
%
Unlucky · P10$01 in 10 end below
Middle · P50$0the coin-flip case
Lucky · P90$01 in 10 end above
Chance of reaching at least
$
What if the return is different?

Same plan, recomputed at nearby yearly returns. Your current rate is highlighted.

Yearly returnYou'd end with
Next step

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Common questions

How does compound interest work?

Your money earns a return, and then that growth earns a return too. Each period the balance grows, and the next period's growth is calculated on the new, larger balance. That snowball is why long time horizons matter more than perfect timing.

What rate of return should I assume?

A common reference is the S&P 500's long-run average of about 10% a year before inflation (roughly 7% after inflation). Bonds have averaged around 4.5%. These are historical averages, not guarantees; real returns vary a lot year to year, so use the sensitivity table to see how nearby rates change the outcome.

Is this calculator adjusted for inflation?

Yes. Set an inflation rate and the "What it's really worth" card shows your ending balance in today's dollars next to the nominal figure, with the gap lost to inflation broken out. It uses the correct real-return relation, (1 + return) ÷ (1 + inflation) − 1, not the rough return − inflation shortcut.

Does it account for fund fees or expense ratios?

Yes. Enter an annual fee (a fund's expense ratio or an advisor's AUM fee) and it's subtracted from your return every year, so it compounds against you the same way growth compounds for you. You'll see the ending balance with and without the fee and the lifetime dollar cost, which is usually far larger than the headline percentage suggests.

What is the Monte Carlo range?

Real markets don't return the same number every year. Turn on the Monte Carlo range and, using your return as the average plus a volatility you choose, it runs 500 randomized paths and reports the unlucky (P10), middle (P50), and lucky (P90) ending balances, plus the probability of reaching your goal. A single smooth projection is closer to a coin-flip than a promise; showing the honest spread is the point.

How often should growth compound?

Match it to where your rate came from. Quoted market averages like "the S&P returns about 10% a year" are yearly figures, so yearly is the honest default. Savings accounts and CDs usually compound monthly or daily; pick that if you're modeling a real account.

Can it solve for the return, contribution, or years I need?

Yes. Pick a goal at the top of the calculator and it will solve for the yearly return, the contribution, the starting amount, or the number of years required to reach it.

Is the investment calculator really free?

Yes, free, no account, no upsells. Every result shows the formula behind it, and you can export the full projection as a spreadsheet.