Same rate, two results
Two savings accounts with the same quoted annual rate but different compounding periods end up with different results. The tool shows the effective annual rate for the method you chose, not just the quoted number.
Leave it alone for ten years — then what?
Compound interest
Estimate how a sum with monthly top-ups grows — plus three things that are easy to overlook: the compounding period, how much is interest versus what you put in, and buying power after inflation.
Why this tool exists
What’s easy to miss
The number that makes compounding click
Beyond the final amount, look at how much of it is interest. The longer the horizon, the more room interest has to grow — as long as the return and contributions hold as assumed.
Money in twenty years isn't today's money
The tool converts the final figure to today’s buying power using the inflation rate you enter. Without that step, future money looks bigger than what it can actually buy.
How it works
What you enter, what you get back
You enter
The money you have, the monthly top-up, the years you will hold it, the annual rate and how often interest compounds (monthly, quarterly, half-yearly, yearly).
It runs period by period
Contributions earn interest for exactly the part of the period they were actually in — paying in at the start of a month earns one month more than at the end.
You read
The final amount, how much you put in versus interest, the effective annual rate, roughly how long it takes the starting sum to double under these assumptions, the value in today’s buying power, and a year-by-year table.
What the tool doesn’t account for
- The rate you enter is an assumption, not a promised return. For deposits, the real result also depends on the bank’s terms and how it calculates interest.
- Results are before tax and fees.
- Real banks accrue interest daily, and term deposits usually do not accept top-ups mid-term.
Sample table
Reading a sample result
One made-up scenario: what the tool returns, and how to read it.
These are illustrative figures, not anyone’s real data. The assumptions are set deliberately high so they match no one’s situation, and are calculated with the app’s own formulas to show how to read the results.
This is not financial advice, nor an offer to lend or invest. To work out your own situation, use the tool in the app.
Sample figures — deliberately inflated
Assumed inputs
- Money you have now
- 7,777,000,000 ₫
- Added every month
- 333,000,000 ₫
- Interest rate
- 13.7% a year
- Compounding
- Every 6 months
- Paid in at
- End of month
- Held for
- 25 years
- Inflation
- 4.4% a year
After 25 years1,007,428,169,291 ₫
Money you put in107,677,000,000 ₫
Interest share89.3%
Effective annual rate14.17% a year
Under these assumptions, the starting sum doubles in about5.2 years
In today's money343,321,991,924 ₫
How the money grows
A few milestones across 25 years — not every year.
| Year | Put in so far | Interest so far | Year-end balance | In today's money |
|---|---|---|---|---|
| Year 1 | 11,773,000,000 ₫ | 1,356,762,426 ₫ | 13,129,762,426 ₫ | 12,576,400,792 ₫ |
| Year 5 | 27,757,000,000 ₫ | 15,521,212,261 ₫ | 43,278,212,261 ₫ | 34,895,290,591 ₫ |
| Year 10 | 47,737,000,000 ₫ | 64,404,610,169 ₫ | 112,141,610,169 ₫ | 72,905,753,169 ₫ |
| Year 15 | 67,717,000,000 ₫ | 178,002,233,846 ₫ | 245,719,233,846 ₫ | 128,804,688,755 ₫ |
| Year 20 | 87,697,000,000 ₫ | 417,129,133,727 ₫ | 504,826,133,727 ₫ | 213,369,262,428 ₫ |
| Year 25 | 107,677,000,000 ₫ | 899,751,169,291 ₫ | 1,007,428,169,291 ₫ | 343,321,991,924 ₫ |
Swipe sideways to see the whole table.
Same 13.7% a year, different compounding
No inflation adjustment; same money, same 25 years.
| Compounding | Effective rate | Final balance | More than yearly |
|---|---|---|---|
| Monthly | 14.59% a year | 1,084,065,101,739 ₫ | 154,384,116,663 ₫ |
| Every 3 months | 14.42% a year | 1,051,943,526,898 ₫ | 122,262,541,822 ₫ |
| Every 6 months | 14.17% a year | 1,007,428,169,291 ₫ | 77,747,184,215 ₫ |
| Yearly | 13.70% a year | 929,680,985,076 ₫ | 0 ₫ |
Swipe sideways to see the whole table.
The highlighted row is the compounding used in the table above.
Work it out for your own situation
In the app you can change every assumption and see the result update right away.