Compound Interest Calculator
Grow savings with compound interest and regular deposits.
Investment Details
Your growth updates instantly as you change any field.
Final balance
$16,288.95
After 10 years, compounded annually.
Balance Growth Over Time
A contribution entered at a different frequency to your compounding frequency is spread evenly into each compounding period — e.g. a $1,200 annual contribution with quarterly compounding adds $300 every quarter.
Year-by-Year Breakdown
| Year | Deposited | Interest earned | Balance |
|---|---|---|---|
| 1 | $10,000.00 | $500.00 | $10,500.00 |
| 2 | $10,000.00 | $1,025.00 | $11,025.00 |
| 3 | $10,000.00 | $1,576.25 | $11,576.25 |
| 4 | $10,000.00 | $2,155.06 | $12,155.06 |
| 5 | $10,000.00 | $2,762.82 | $12,762.82 |
| 6 | $10,000.00 | $3,400.96 | $13,400.96 |
| 7 | $10,000.00 | $4,071.00 | $14,071.00 |
| 8 | $10,000.00 | $4,774.55 | $14,774.55 |
| 9 | $10,000.00 | $5,513.28 | $15,513.28 |
| 10 | $10,000.00 | $6,288.95 | $16,288.95 |
How to Calculate Compound Interest
Enter your starting deposit, annual interest rate, how long you're investing for, and how often interest compounds — annually, semi-annually, quarterly, monthly, weekly or daily. Add an optional regular contribution to see how steady deposits accelerate your growth.
The Formula
where r = annual rate ÷ compounding periods per year, and n = years × compounding periods per year. With regular contributions, each one is added and compounds for the periods remaining.
Worked Example
$10,000 deposited at 5% per year, compounded annually for 10 years with no extra contributions, grows to $16,288.95 — that's $6,288.95 in interest. Add a $200 monthly contribution to a $5,000 deposit at 6% compounded monthly over 10 years instead, and the balance reaches $41,872.85: $24,000 of that is your own contributions, with $12,872.85 earned in interest.
Nominal Rate vs Effective Annual Rate (EAR)
The nominal rate is the annual rate you're quoted — 6%, say. The effective annual rate (EAR) is what that rate actually works out to once compounding frequency is factored in: 6% compounded monthly has an EAR of about 6.17%, because interest is calculated and added twelve times a year instead of once. The more frequently interest compounds, the larger the gap between nominal and effective rates.
Frequently Asked Questions
- How do I calculate compound interest yearly?
- Set the compounding frequency to "Annually" above. The formula is Final Balance = Principal × (1 + Annual Rate)^Years — so $10,000 at 5% for 10 years, compounded yearly, grows to $16,288.95, which is $6,288.95 in interest.
- What's the difference between annual and compounded annually?
- They mean the same thing here: interest is calculated and added to your balance once per year, so next year's interest is earned on last year's interest as well as your original deposit — that's what makes it "compound" rather than simple interest.
- How do I use a compound interest calculator with monthly or annual contributions?
- Enter your regular deposit in the "Regular contribution" field, then choose whether you're contributing monthly or annually and whether each contribution lands at the start or end of a compounding period. The calculator works out your total deposited, total interest earned, and final balance, with a year-by-year table showing the split.
- Can I calculate compound interest with quarterly compounding?
- Yes — set "Compounding frequency" to Quarterly. If your contribution is entered as a monthly or annual amount, it's automatically spread evenly into each quarter so the two settings work independently of each other.
- How do I find the compound interest rate / cumulative interest rate?
- This calculator shows two rates: your nominal annual rate (what you entered) and your effective annual rate (EAR) — the true annual return once compounding is accounted for. For example, a 6% rate compounded monthly has an effective annual rate of about 6.17%, slightly higher than the nominal rate because interest compounds more often than once a year.
- What is a compound growth calculator used for?
- A compound growth calculator projects how a starting amount (and any regular contributions) grows over time when returns are reinvested rather than withdrawn — common uses include savings accounts, term deposits, managed funds and superannuation balances, anywhere interest or returns compound rather than being paid out as simple interest.
- Does this calculator handle increasing contributions?
- This version uses a fixed regular contribution amount for the full period rather than one that increases each year. If your contributions step up annually (e.g. with a pay rise), run the calculator in stages — once for each contribution level and time period — and carry the final balance from one stage into the next as the starting principal.
- What's the formula for compound interest with contributions?
- For a lump sum alone it's Final Balance = Principal × (1 + r)ⁿ, where r is the rate per compounding period and n is the number of periods. With regular contributions added each period, it becomes Final Balance = Principal × (1 + r)ⁿ + Contribution × [((1 + r)ⁿ − 1) ÷ r] for contributions at the end of each period (slightly more if added at the start, since they then earn an extra period of interest).