Use this compound interest calculator to marvel at the power of compounding.
About these results
- The results are estimates. We’ve tested the calculator across a wide range of inputs, but we can’t guarantee every result is free of errors, so use it as a guide rather than an exact figure.
- Enter plain numbers only. Shorthand such as “10k”, or a “%” sign in the rate box, won’t be read correctly.
- If a result looks unusually high or low, check the rate and the compounding frequency first.
- Regular deposits are assumed to be made at the end of each period, and results are before fees, taxes, and inflation.
- Results are illustrations based on the rate you enter, not a forecast or a guarantee. Investments can fall in value as well as rise.
- Don’t rely on the calculator alone for important financial decisions. Check key figures with your bank, CPF, or a licensed financial adviser representative before acting.
How to Use This Compound Interest Calculator
There are six fields to fill in:
- Initial investment. The lump sum you start with. Leave it at $0 if you’re only making regular deposits.
- Regular investment amount. What you add each time, such as $500 a month.
- Frequency of regular investment. How often you add it, for example Monthly if you save from your salary each month.
- Length of investment period. In years. Decimals work (2.5 for two and a half years), and only deposits you’d have made by then are counted.
- Annual interest rate. The yearly rate as a percentage, so 3 for 3%. If a product quotes a monthly rate, multiply it by 12 first.
- Compounding frequency. How often interest is added to your balance. See the next section if you’re unsure.
The result updates as soon as you click out of a field.
SIDE NOTE
A policy bought years ago. Savings in three places. A will that's still on the to-do list.
None of it is wrong. It's just not a plan yet.
There's an order that turns the pieces into one system, and it doesn't require becoming a finance expert. Here's the order, in 7 steps, so you know what to sort out first.
What Is Compound Interest?
Compound interest is interest earned on your original money and on the interest it has already earned. Every time interest is added, the next round is worked out on a slightly bigger balance.
Simple interest is only ever paid on the original sum. Here’s how the two compare for $20,000 left at 4% a year for 25 years:
| Type of interest | Balance after 25 years |
|---|---|
| Simple interest | $40,000.00 |
| Compound interest (yearly) | $53,316.73 |
Compounding adds $13,316.73, even though you never put in any more money.
Which Compounding Frequency Should You Choose?
Choose how often your money actually has interest added to it. If you’re not sure, Annually is the safer choice, because it won’t overstate your result.
| Where your money is | Setting to choose |
|---|---|
| CPF accounts | Annually |
| Bank savings accounts | Usually Monthly (check your bank’s terms) |
| Fixed deposits | Match the deposit’s term if you renew with the interest added |
| Singapore Savings Bonds | Doesn’t compound unless you reinvest the interest yourself |
| Stocks, ETFs, and funds | Annually |
CPF interest is worked out monthly but credited and compounded once a year, which is why Annually is the right setting.
Singapore Savings Bonds work differently. The interest is paid out to you every six months instead of being added to the bond, so it only compounds if you invest it again yourself.
For investments, returns are usually quoted as an average yearly figure that already includes compounding. Choosing a more frequent setting would count it twice.
Why the setting matters
Say you want to see what $10,000 grows to over 30 years at an average return of 8% a year:
- With Annually selected, the result is $100,626.57.
- With Daily selected, it’s $110,202.78.
The second figure is almost $9,600 too high. 8% compounded daily works out to about 8.33% a year, so the calculator ends up using a higher rate than you meant.
When a product really does compound more often, such as a savings account, the effect is small. $50,000 at 3% for 10 years ends at $67,195.82 compounded yearly and $67,492.11 compounded daily, a difference of under $300.
What Interest Rate Should You Enter?
Use the rate your money actually earns. For anything where the rate isn’t fixed, run the calculator at a few different rates and look at the range.
- CPF. The current rates for each account are published on the CPF website and in our guide to CPF interest rates. CPF also pays extra interest on part of your balances, which the calculator doesn’t include, so your actual balance may come out higher.
- Bank deposits and government securities. Rates on fixed deposits, Singapore Savings Bonds, and T-bills change over time, so check the latest figure before you enter it. The rate you get today may not be the rate you get when you renew.
- Investments. Stocks, ETFs, and funds don’t pay a set rate, and their returns can be negative in some years. Try a few rates, say 3%, 5%, and 7%, and treat the results as a range rather than a target.
Small differences in rate add up over long periods. $10,000 left for 30 years with yearly compounding grows to $20,975.68 at 2.5%, but $32,433.98 at 4%.
QUICK CHECK
Can you answer these three questions?
1) If something happened to you tomorrow, how much would your family receive?
2) At 65, what monthly income will your savings and investments pay you?
3) If you never get round to a will, who inherits what, and in what proportion?
Most people manage one at best. Not because they're careless, but because nobody has shown them which order to tackle things in.
That order exists. Work through your finances in this sequence, from income and protection through to investments and estate planning.
How Time and Regular Deposits Change the Result
Here’s what $500 a month grows to with yearly compounding:
| Years | You put in | At 2.5% | At 4% | At 6% |
|---|---|---|---|---|
| 10 | $60,000 | $67,987 | $73,348 | $81,237 |
| 20 | $120,000 | $155,016 | $181,921 | $226,719 |
| 30 | $180,000 | $266,421 | $342,635 | $487,256 |
Over 10 years, the difference between 2.5% and 6% is about $13,000. Over 30 years, it’s more than $220,000.
The longer your money stays invested, the more of the final balance comes from interest rather than from your own deposits. That’s why starting early often does more than hunting for a slightly higher rate.
The Rule of 72
For a quick estimate, divide 72 by the yearly rate to get roughly how many years your money takes to double. At 4%, that’s about 18 years. At 6%, about 12.
It works for debt too. At an interest rate of 24% a year, an unpaid balance roughly doubles in about three years. That’s one reason to keep an emergency fund, so a surprise bill doesn’t end up on a credit card.
How the Calculator Works (Formula)
The calculator adds two things together: the growth of your initial investment, and the growth of each regular deposit from the date it’s made.
Future value = P × (1 + r/n)^(n × t) + A × [(1 + i)^k – 1] ÷ i × (1 + r/n)^(n × (t – k/p))
Where:
- P = initial investment
- A = regular amount added at the end of each period
- r = annual interest rate (as a decimal)
- n = number of times interest is compounded per year
- p = number of regular deposits per year
- t = number of years
- i = rate per deposit period, which is (1 + r/n)^(n/p) – 1
- k = number of whole deposits made in t years, which is p × t rounded down
The rate per deposit period (i) lets you deposit at a different frequency from the compounding. The last part of the formula covers any time left after the final deposit, when the balance keeps growing with nothing added. At 0%, the result is simply your initial investment plus your total deposits.
To check a result in Excel or Google Sheets, use the FV function when your deposit and compounding frequencies are the same. For example, =FV(5%/12, 120, -500, -10000) returns $94,111.23, which matches the calculator for $10,000 plus $500 a month at 5%, compounded monthly, over 10 years.
Why other calculators may show a slightly different number
When deposits are made more often than interest is added (monthly deposits with yearly compounding, for example), calculators handle the in-between months in different ways. Some give those deposits no interest until the year ends, which produces a lower figure.
This calculator converts the yearly rate into an equivalent rate for each deposit period, a common method that lets every deposit earn interest from the day it’s made. We’ve checked it against a separate deposit-by-deposit calculation across a wide range of inputs, and the results match.
What This Calculator Doesn’t Show You
The calculator grows your money in a straight, predictable way. In practice, a few other things affect what you end up with:
- Inflation. Your future balance will buy less than the same amount buys today. At 2% inflation a year, $100,000 in 20 years has about the buying power of $67,000 now. See our page on inflation in Singapore for past rates.
- Fees and taxes. Fund fees, platform fees, and sales charges reduce what’s left to compound, and even small yearly fees add up over decades.
- Ups and downs. The calculator grows your money at the same rate every year. Investments don’t, and a poor year close to when you need the money can hurt more than the average suggests.
- Changing rates. Rates on new deposits and bonds move with the market, and CPF rates are reviewed regularly, so today’s rate may not apply for the whole period you enter.
- Deposit timing. Deposits are assumed to land at the end of each period. Investing at the start of each period would give a slightly higher result.
The calculator and examples on this page are for general information only. They don’t take your personal circumstances into account and aren’t a recommendation to buy any product.
While we’ve taken care to make the calculator accurate, it may contain errors, and SmartWealth isn’t responsible for decisions made based on its results. Before making investment decisions, consider speaking with a licensed financial adviser representative.
What’s Next?
A compound interest figure means more when you know what the money is for. Our retirement calculator and education fund calculator work out how much you need and by when.
To see where saving and investing fit alongside protection, CPF, and estate planning, follow the order of steps in personal financial planning. FinSnap then puts your goals, savings, CPF, and insurance in a single file.
If you’d rather have a professional go through the numbers with you, our comprehensive financial planning session covers your savings, CPF, insurance, and investments at no cost.
BEFORE YOU GO
Articles can tell you what generally makes sense. They can't see your policies, your CPF, or your plans.
FullCircle is our comprehensive financial planning session. A licensed consultant goes through what you have, shows you the gaps and overlaps, and tells you what to prioritise across protection, retirement, and estate planning.
It's complimentary, takes about 45 minutes, and if nothing needs changing, we'll say so.