Savings and loan tools
Compound Interest Calculator
Calculate monthly compound interest with regular contributions. See your projected balance, total deposits and interest, then download a monthly savings schedule.
Find another tool
This tool needs JavaScript. If the controls don’t appear, check your connection, enable JavaScript and reload this page.
How to use this tool
1. Enter your starting balance, nominal annual interest rate and time period. Choose months for a partial-year term. The rate is entered by you, not fetched from a bank.
2. Set your monthly contribution, or 0 for a lump sum only. Choose whether deposits arrive at the beginning or end of each month.
3. Calculate to separate contributions from interest and inspect the yearly breakdown. Copy the summary, print a report or download every month as CSV.
How monthly compounding works
Each month earns interest on the existing balance, including interest credited in earlier months. The monthly rate is the nominal annual percentage divided by 1,200. End-of-month deposits are added after that month’s interest; beginning-of-month deposits earn interest immediately.
Worked example
A starting balance of 10,000 at a nominal 12% annual rate earns 100 in the first month. Over two months, with 100 deposited at each month-end, the balance becomes 10,402: 10,200 contributed and 202 interest. Moving deposits to the beginning of the month gives 10,404.01.
Questions and assumptions
Nominal rate versus effective yield
The effective annual yield includes twelve months of compounding: (1 + annual rate / 1,200)^12 − 1. This tool shows it separately. A quoted APY or effective yield already includes compounding and must not be entered directly as the nominal rate.
Growth is an assumption, not a forecast
The projection holds your chosen rate and contribution constant. It is not a forecast of investment returns. Starting balances can be 0–10 million and monthly deposits 0–1 million. Calculations keep full precision, while the display and CSV round each figure to cents. Results above 1 trillion are rejected.
What does this estimate leave out?
This is an illustration, not a quote or financial advice. It assumes a fixed nominal annual rate divided by 12 and monthly compounding. It excludes fees, tax, inflation, rate changes and currency conversion. Actual products can use daily interest, different rounding and eligibility conditions. Check the terms of your account or loan; the tool does not assess affordability or recommend a product.
Supported inputs
Choose AUD, USD, GBP, EUR, CAD or NZD as a display label; this does not convert values. Enter amounts without commas or currency signs, with up to two decimal places. Use a rate from 0% to 60% and a term of 1–600 whole months or 1–50 whole years. Negative rates and withdrawals are outside this model.
Sources and further reading
Built and maintained by Custom Logic. Page updated .