Compound interest & finance calculator
By MoneyBees
See what your savings grow to with compound interest, or solve for the monthly amount, the years or the return you need to hit a target. Set the compounding frequency, add monthly top-ups and adjust for inflation, then test it against CPF, SSB and T-bill rates.
Calculator
What do you want to solve for?
Inputs
Per monthly period
Solving for this, so the input is ignored
Nominal annual rate of return
Advanced
End: deposit after interest is applied (typical for savings). Beginning: deposit before interest (typical for annuities).
Adjust for inflation
Show all values in today's dollars
Solving for Future value
$462,290
7.00% a year compounded monthly is an effective 7.229% a year.
Total contributed
$160,000
PV + all payments
Interest earned
$302,290
growth from compounding
Ending balance
$462,290
after 25.0 yrs
Growth over time
Stacked area: grey = your starting amount, blue = contributions added over time, gold = interest earned. Top of the stack = total balance at that point.
Year-by-year breakdown
| Year | Contributions | Interest | Balance |
|---|---|---|---|
| 0 | $10,000 | $0 | $10,000 |
| 1 | $16,000 | $919 | $16,919 |
| 2 | $22,000 | $2,339 | $24,339 |
| 3 | $28,000 | $4,294 | $32,294 |
| 4 | $34,000 | $6,825 | $40,825 |
| 5 | $40,000 | $9,973 | $49,973 |
| 6 | $46,000 | $13,782 | $59,782 |
| 7 | $52,000 | $18,299 | $70,299 |
| 8 | $58,000 | $23,578 | $81,578 |
| 9 | $64,000 | $29,671 | $93,671 |
| 10 | $70,000 | $36,639 | $106,639 |
| 11 | $76,000 | $44,544 | $120,544 |
| 12 | $82,000 | $53,455 | $135,455 |
| 13 | $88,000 | $63,443 | $151,443 |
| 14 | $94,000 | $74,587 | $168,587 |
| 15 | $100,000 | $86,971 | $186,971 |
| 16 | $106,000 | $100,683 | $206,683 |
| 17 | $112,000 | $115,820 | $227,820 |
| 18 | $118,000 | $132,486 | $250,486 |
| 19 | $124,000 | $150,790 | $274,790 |
| 20 | $130,000 | $170,851 | $300,851 |
| 21 | $136,000 | $192,796 | $328,796 |
| 22 | $142,000 | $216,760 | $358,760 |
| 23 | $148,000 | $242,892 | $390,892 |
| 24 | $154,000 | $271,345 | $425,345 |
| 25 | $160,000 | $302,290 | $462,290 |
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Simple vs compound interest
S$10,000 at 5% a year, no extra contributions. Compounding pulls ahead and the gap widens over time.
| After | Simple interest | Compound interest |
|---|---|---|
| 1 year | S$10,500 | S$10,500 |
| 5 years | S$12,500 | S$12,763 |
| 10 years | S$15,000 | S$16,289 |
| 20 years | S$20,000 | S$26,533 |
Compound interest formula: A = P(1 + r/n)^(nt). Rule of 72: at 5%, money doubles in about 14 years.
How this works
This is a 5-variable time-value-of-money (TVM) solver. The five variables are:
- PV (present value): your starting balance
- PMT (payment): what you add each period
- FV (future value): the ending balance
- N: years times the payment frequency
- I/Y: the yearly interest rate
Fill in any four and we solve for the fifth, using the standard TVM equation:
FV = PV x (1+i)n + PMT x [(1+i)n - 1] / i x adj
When payment frequency (P/Y) differs from compounding frequency (C/Y), we convert to an equivalent rate per payment period using the effective annual rate, the same convention as the TI BA II Plus and HP 10bII.
Inflation adjustment uses the real return formula: real = (1+nominal)/(1+inflation) - 1. All displayed dollar values become today's dollars.
7% a year at each compounding frequency
What S$10,000 grows to in 25 years with no top-ups.
| Compounded | Effective yearly rate | After 25 years |
|---|---|---|
| Annually | 7.000% | $54,274 |
| Semi-annually | 7.122% | $55,849 |
| Quarterly | 7.186% | $56,682 |
| Monthly | 7.229% | $57,254 |
| Daily | 7.250% | $57,536 |
The effective rate is what the nominal rate earns in a year once interest is added to the balance. The gap between monthly and daily is small. The rate itself matters far more.
Singapore rates to try in the calculator
| Where | Rate a year | As of |
|---|---|---|
| CPF Ordinary Account | 2.50% | 1 Oct to 31 Dec 2026 |
| CPF Special, MediSave and Retirement Accounts | 4.00% | 1 Oct to 31 Dec 2026 |
| Singapore Savings Bond GX26120A, 10-year average | 2.39% | Issued 1 Dec 2026 |
| 6-month T-bill cut-off yield | 1.86% | Auction 4 Nov 2026 |
SSB and T-bill figures are the latest MAS results and change with each issue. CPF pays extra interest on the first S$60,000 of your balances, which is not in these rates.
Worked examples
Starting 10 years earlier. S$200 a month at 6% a year, compounded monthly, grows to about S$398,298 over 40 years. The same S$200 a month over 30 years reaches about S$200,903. The extra 10 years cost S$24,000 more in deposits and nearly double the result.
Compounding frequency. S$10,000 at 5% a year for 20 years reaches S$26,533 compounded yearly and S$27,126 compounded monthly. The effective rate goes from 5.000% to 5.116%.
Working backwards. If you want S$1,000,000 in 25 years at 7% a year and you start with S$10,000, set the calculator to solve for the periodic payment and it shows what you need to put in each month.
Sources
Figures checked 3 Oct 2026.
Frequently asked questions
What is compound interest?
Interest earned on your interest. Each period the interest is added to your balance, and the next period's interest is worked out on that bigger balance. Simple interest pays only on the amount you started with. S$10,000 at 5% a year grows to S$26,533 in 20 years with yearly compounding, against S$20,000 with simple interest.
What is the compound interest formula?
A = P(1 + r/n)^(nt). P is the starting amount, r the yearly rate as a decimal, n the number of times interest is added each year and t the number of years. Regular top-ups add a second part: PMT x ((1 + i)^m - 1) / i, where i is the rate per period and m the number of deposits.
Does compounding frequency matter?
A little. 5% a year compounded monthly works out to 5.116% a year, against 5.000% compounded yearly. Over 20 years on S$10,000 that is S$27,126 against S$26,533. The rate you earn and how long you stay invested matter much more than how often interest is added.
How do I work out the monthly amount I need to reach a target?
Set the calculator to solve for the periodic payment. Enter your target as the future value, your starting amount, the years and the yearly return. The calculator shows the amount to put in each month. You can solve for the years or the return you need the same way.
What interest rate should I use?
Use a rate you can point to. In Q4 2026 the CPF Ordinary Account pays 2.5% a year and the Special, MediSave and Retirement Accounts pay 4%. The latest Singapore Savings Bond and T-bill rates are in the table on this page. For shares or funds, any rate is an assumption, and real returns go up and down from year to year.
Can I use this calculator for my CPF savings?
For a rough idea, yes. Enter your balance, your monthly contribution and 2.5% for the OA or 4% for the SA. CPF adds interest monthly and credits it once a year, and pays extra interest on your combined balances (1% on the first S$60,000 below 55; from 55, 2% on the first S$30,000 and 1% on the next S$30,000), so your real CPF balance will be a little higher.
Does the calculator account for inflation?
Only if you turn it on. Switch on Adjust for inflation and enter the rate you expect. The calculator then uses the real return, (1 + nominal) / (1 + inflation) - 1, and shows every figure in today's dollars.
What is the Rule of 72?
A quick check on how long money takes to double: 72 divided by the yearly return. At 6% that is about 12 years, at 4% about 18 years. It is close for rates between 2% and 10%. The calculator gives the exact figure if you solve for the years.
What is the difference between end and beginning of period?
End of period means each deposit goes in after that period's interest, which is how most savings plans work. Beginning of period means the deposit earns interest for the period it goes in, so the final balance is a little higher.
How we calculate this
- We turn the yearly rate into a rate for each payment period. When payments and compounding happen at the same frequency, that is the yearly rate divided by the number of periods: 7% / 12 = 0.5833% a month. When they differ, we first find the effective yearly rate, (1 + r/n)^n - 1, and convert it to the payment period. Financial calculators such as the TI BA II Plus use the same convention.
- We grow the starting amount: PV x (1 + i)^n, where i is the rate per period and n is years times payments a year.
- We add the regular payments: PMT x ((1 + i)^n - 1) / i. A payment made at the start of each period earns one more period of interest, so for start-of-period payments that total is multiplied by (1 + i).
- The ending balance is the two parts added together. Interest earned is that balance minus everything you put in. The year-by-year table runs the same sum one period at a time.
- With the inflation switch on, we replace your rate with the real return, (1 + rate) / (1 + inflation) - 1, so every dollar figure is in today's money.
- To solve for the starting amount, the payment or the years, we rearrange the same equation. The rate has no direct formula, so the calculator narrows it down by repeated halving until both sides match.
- The Singapore rates in the table above come from CPF Board for CPF interest and from MAS auction results for T-bills and Singapore Savings Bonds. Type one of them in as your rate to compare. Source: CPF Board: interest rates, 1 Oct to 31 Dec 2026
Rounding
The calculator keeps full precision through every period and rounds only what it shows, to the nearest dollar. Banks credit interest in whole cents, often daily or monthly, so a real statement can differ from this result by small amounts.
Worked example: the default case
- You start with S$10,000 and add S$500 at the end of every month for 25 years, at 7% a year compounded monthly. That is 300 monthly periods at 0.5833% each.
- Growth factor: (1 + 0.07 / 12)^300 = 5.7254.
- The starting amount grows to S$10,000 x 5.7254 = S$57,254.
- The payments grow to S$500 x (5.7254 - 1) / 0.005833 = S$405,036.
- Ending balance: S$57,254 + S$405,036 = S$462,290.
- You put in S$10,000 + 300 x S$500 = S$160,000, so the interest earned is S$462,290 - S$160,000 = S$302,290.
What this calculator does not cover
- Returns that change from year to year. The calculator holds one rate for the whole period, so it cannot show the ups and downs of a share or bond fund.
- Fees and charges, which come off the return before it compounds.
- Tax on returns, where it applies.
- CPF's extra interest on the first S$60,000 of your combined balances.
- Payments that rise each year, or months you miss.
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These calculators provide general estimates for educational purposes only and are not personalised financial advice. Results may rely on rates and rules that change over time, so verify against official sources (IRAS, CPF Board, HDB, MAS) or consult a licensed financial adviser before making decisions.
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