Compound Interest Calculator with Growth Chart
This free compound interest calculator shows investors, savers, and retirement planners exactly how an initial deposit grows over time. Adjust the principal, annual rate, time period, monthly contribution, and compounding frequency — a live line chart and year-by-year table update instantly so you can visualise the power of compounding.
Year-by-Year Breakdown
| Year | Balance | Interest Earned | Total Contributions |
|---|
How to Use the Compound Interest Calculator
- Set the principal — your starting deposit or investment amount.
- Enter the annual interest rate offered by your bank, fund, or expected from the market.
- Choose the time period in years (up to 40).
- Add a monthly contribution if you plan to invest regularly — even small amounts make a dramatic difference.
- Select a compounding frequency: daily, monthly, quarterly, or annually.
- Read the final balance, total contributions vs interest breakdown, and the line chart — then download the CSV if needed.
The Compound Interest Formula
For a lump sum: A = P(1 + r/n)^(nt)
With regular monthly contributions (PMT): A = P(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)]
- P = Principal (initial investment)
- r = Annual interest rate as a decimal (e.g. 0.07 for 7%)
- n = Compounding periods per year (12 = monthly, 365 = daily)
- t = Time in years
- PMT = Monthly contribution amount
Key Features
- Live canvas line chart comparing growth with and without monthly contributions.
- Year-by-year breakdown table showing balance, annual interest earned, and total contributions.
- Four compounding frequencies: daily (365×), monthly (12×), quarterly (4×), annually (1×).
- Interest vs contributions split shown in stat cards — see exactly how much your money worked for you.
- Download full dataset as CSV for use in Excel or Google Sheets.
- Copy a formatted text summary to your clipboard for sharing or record-keeping.
Use Cases
Plan a Retirement Savings Strategy
Enter your current savings balance, a realistic annual return (6–7% for a diversified portfolio), your years to retirement, and a monthly contribution. The calculator shows whether you are on track for your retirement income goal — and how increasing contributions by even $100 per month changes the outcome. Knowing your take-home pay after deductions helps you decide how much you can realistically put aside each month.
Compare Savings Account Offers
Two accounts may quote similar rates but compound at different frequencies. Run both in the calculator to see the actual dollar difference over your intended savings period. For large balances, even the difference between monthly and daily compounding adds up.
Model a College Education Fund
A parent investing $5,000 today plus $300 per month at 6% over 18 years accumulates over $120,000 — enough to cover a significant portion of university costs in many countries, without taking on student debt.
Understand the Cost of Debt vs the Value of Investment
Compound interest works against you on loans and credit cards just as powerfully as it works for you on investments. Comparing the compounding curves side by side can motivate paying down high-interest debt before investing in low-return vehicles.
FAQ's
Simple interest is earned only on the original principal. Compound interest is earned on the principal plus all accumulated interest. On $1,000 at 10% for 3 years: simple = $300 total interest; annual compound = $331. The gap widens dramatically over longer periods and higher rates.
Lump sum: A = P(1 + r/n)^(nt). With monthly contributions: A = P(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)]. Variables: P = principal, r = annual rate as decimal, n = compounding periods per year, t = years, PMT = monthly contribution.
More frequent compounding produces higher returns because interest is added to the balance — and starts earning interest — more often. On $10,000 at 7% for 20 years: annual compounding = $38,697; daily compounding = $40,064. The biggest gain comes from moving from annual to monthly; going from monthly to daily adds only a small further increment.
Divide 72 by the annual interest rate to estimate how many years it takes to double your money. At 6%: 72 ÷ 6 = 12 years. At 9%: 8 years. At 12%: 6 years. It is a quick mental estimate — the mathematically exact answer uses the natural logarithm, but the Rule of 72 is accurate enough for planning purposes.
The S&P 500 has returned approximately 10% annually before inflation (roughly 7% after). Financial planners typically use 5–7% for diversified portfolios as a conservative baseline. Always model a range of 5%, 7%, and 10% to understand best-case, base-case, and optimistic outcomes.
Enormously. A $10,000 investment at 7% for 20 years without contributions grows to about $40,000. Adding $200 per month pushes the final balance past $145,000 — more than three times higher — because every contribution itself starts compounding from the day it is deposited.
The nominal rate is the stated rate before accounting for intra-year compounding. The effective annual rate (EAR) reflects what you actually earn when compounding occurs multiple times per year. Formula: EAR = (1 + r/n)^n − 1. A 12% nominal rate compounded monthly is an effective rate of 12.68%.
Yes. Click "Download CSV" below the chart. The file includes columns for Year, Balance, Interest Earned (that year), and Total Contributions, and opens directly in Excel or Google Sheets for further charting or analysis.
Related Tools
Compound interest is the single most powerful concept in personal finance — Albert Einstein reportedly called it the eighth wonder of the world. Whether you are building a retirement nest egg, saving for a house deposit, or modelling a business investment, understanding exactly how your balance grows year by year puts you in control of your financial future. To evaluate the profitability of any of those investments in percentage terms, pair this tool with the ROI calculator. Toolaroid's compound interest calculator is free, private, and works entirely in your browser without any account or data collection.