Compound Interest Calculator
See how your money grows with regular contributions and compounding returns. Adjust the inputs to project your investment over time.
Default 7% is an illustrative long-run equity assumption — adjust to your own expectation.
Final value
$300,851
After 20 years at 7% p.a.
Total contributions
$130,000
Total gains
$170,851
Growth multiple
2.31×
Estimates only, assuming a constant rate compounded monthly. Actual investment returns vary and may be negative.
| Year | Contributions | Gains | 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 |
How compound interest builds wealth
The earlier and more consistently you invest, the more the compounding effect works in your favour. Each month your balance earns a return, and that return then earns its own return — a snowball that accelerates the longer you stay invested.
Use this calculator to compare scenarios: a larger initial amount, a higher monthly contribution, a longer time horizon, or a different expected return. Small, regular contributions over decades often outperform a large one-off sum invested late.
Tips for using the results
Treat the return rate as an assumption rather than a promise. For a real (inflation adjusted) view, reduce your rate by your inflation expectation. For Singapore-specific safe options, see our Singapore Savings Bonds and T-Bill calculators; to plan regular investing, try the dollar-cost averaging calculator.
Frequently asked questions
What is compound interest?
Compound interest is the interest you earn on both your original money and on the interest it has already earned. Over time this “interest on interest” effect can grow your savings far faster than simple interest.
How is the final value calculated?
This calculator compounds monthly using FV = P(1 + r)ⁿ + PMT × [((1 + r)ⁿ − 1) / r], where P is your initial amount, PMT is your monthly contribution, r is the monthly rate (annual rate ÷ 12) and n is the number of months.
What return rate should I use?
It depends on what you invest in. A diversified global equity portfolio has historically returned roughly 7% a year over the long run, while safer options like Singapore Savings Bonds or fixed deposits return less. The 7% default is an illustrative assumption — set it to your own expectation, and remember returns are never guaranteed.
Does this account for inflation?
No — the result is a nominal figure. To gauge real spending power, subtract an inflation assumption (around 2% a year for Singapore) from your return rate before entering it.