Ruki Portfolio
Portfolio projection
What would happen to your portfolio if you added a contribution every month for a few years. It's a compound interest calculation on assumptions you choose, not a market forecast.
What it is
This tool calculates how a sum of capital would grow if you kept adding a periodic contribution and the whole thing earned a given rate over a given term.
In Ruki it starts from your current portfolio, not from a made-up number. That's the point: instead of playing with hypothetical capital, you see what would happen to what you already have.
You set the three variables
The annual rate. The return assumption you want to run the numbers with. Ruki doesn't suggest or estimate it: you choose it, and you can change it as many times as you like to see how the result changes.
The monthly contribution. How much you could add each month.
The term. In years, or up to a specific date: your sixtieth birthday, the year you want to buy something, whatever you're looking at.
On the whole portfolio or on one goal
You can run the calculation on your whole portfolio or on just one of your goals. If you're building up a travel fund, you look only at that one: the starting point becomes that goal's capital and not your portfolio total.
What it's NOT
It's not a prediction. Ruki doesn't know how much your investments will return, and nobody does: the rate you use is your assumption, not a market forecast.
The result isn't a promise or an attainable target: it's the arithmetic answer to “what would happen if this assumption held exactly?”. In reality returns vary from year to year, can be negative, and past returns don't guarantee future ones.
Ruki doesn't give recommendations or financial advice. This tool is for understanding the effect of compound interest and of consistent contributions, not for deciding what to invest in.
So what is it for
For sizing up the effect of compound interest, which over ten or twenty years is hard to intuit. By putting in your own numbers and moving one variable at a time you see how much each one weighs: the contribution, the rate and, above all, the term.
Try it here
You put in the numbers. It's the same math Ruki does inside the app, the difference being that there the starting capital comes from your real portfolio and here you type it in by hand.
With that portfolio and that same rate, at the end of the term you'd get an income of — a year, or — a month.
Put simply: after — you'd have —. If you leave that capital invested, stop contributing every month and it keeps returning the — you entered above, you'd receive — every month without touching the capital: that — is still yours.
The monthly income is what the capital generates in one month, not the annual figure divided by twelve: withdrawing that each month leaves the capital intact. And all of this is a calculation on assumptions you chose, not a market projection or a promise of returns.
The formula
Nothing is hidden. The starting capital compounds over the full term, and each monthly contribution compounds for the time it has left from the moment it goes in:
FV = C0 · (1 + i)n + A · (1 + i)n − 1 i
- C0: the capital you start with.
- A: each month's contribution.
- n: the number of months, that is, the years times twelve.
- i: the monthly rate, derived from the effective annual rate (TEA) as i = (1 + TEA)1/12 − 1.
In Ruki the starting capital comes from your real portfolio, without you typing it in.
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