Compound Interest Calculator
Calculate investment growth with compound interest
Beginning-of-period contributions earn one extra period of interest.
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What is Compound Interest Calculator?
The Compound Interest Calculator is a free online tool that projects how an investment grows over time when interest is reinvested. You enter an initial investment, an optional recurring contribution, an annual interest rate, a number of years, and how often interest compounds — annually, semi-annually, quarterly, monthly, weekly, daily, or continuously. You can set the contribution frequency (monthly or annual) and choose whether contributions land at the beginning or the end of each period, switch the currency symbol, and optionally adjust for inflation to see the real, in-today's-money value. The tool then shows the projected future value, the total you contributed, the total interest earned, and a real (inflation-adjusted) value when enabled, plus a growth chart and a year-by-year breakdown. Because compounding adds interest on top of previous interest, even modest regular contributions can grow substantially over long periods. Everything runs instantly in your browser with no signup.
How to use Compound Interest Calculator?
Estimating long-term growth takes only a few seconds:
- 1 Pick your currency, then enter your initial investment — the lump sum you are starting with.
- 2 Choose a contribution frequency (none, monthly, or annual), enter the contribution amount, and set whether each contribution is made at the beginning or end of the period.
- 3 Set the annual interest rate as a percentage, the number of years to project, and how often interest compounds — annually, semi-annually, quarterly, monthly, weekly, daily, or continuously. More frequent compounding produces slightly higher returns for the same rate.
- 4 Optionally tick Adjust for inflation and enter an inflation rate to reveal the real value in today's money. The future value, total contributions, total interest, chart, and year-by-year table all update instantly.
Why use this tool?
Compound interest is one of the most powerful forces in personal finance, but it is hard to picture without a calculator. Seeing the future value next to the total you actually contributed makes the impact of time and reinvested returns clear at a glance. The optional inflation adjustment is especially useful: a large nominal balance decades from now may buy far less than it appears, and the real-value figure puts the projection in today's terms. The year-by-year breakdown helps you understand how growth accelerates in later years, while adjusting the rate, contribution timing, or compounding frequency lets you compare scenarios side by side. This is useful for planning savings goals, retirement contributions, or education funds. Because the projection runs locally in your browser, your figures are never uploaded, and you can experiment freely and privately with different assumptions.
Examples
Start with $10,000, add $500 per month at 7% compounded monthly for 10 years, and the tool projects roughly $106,639 — about $70,000 contributed and $36,639 in interest.
A $1,000 lump sum at 5% for 10 years grows to about $1,628.89 compounded annually, but to $1,648.72 with continuous compounding (the Pe^rt limit).
Enable inflation at 3% on a 10-year projection: a nominal $19,672 balance is shown as roughly $14,637 in today's purchasing power.
Frequently Asked Questions
Is the Compound Interest Calculator free?
Yes. It is completely free, with no signup, no limits, and no account required. You can run as many projections as you like.
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal, while compound interest is calculated on the principal plus all previously accumulated interest, which makes the balance grow faster over time.
What is continuous compounding?
Continuous compounding is the mathematical limit of compounding infinitely often, given by the formula future value = principal × e^(rate × time). It produces the highest balance for a given annual rate, just slightly above daily compounding.
What does the inflation adjustment do?
When enabled, it discounts the projected balance by the inflation rate you enter to show the real value in today's money — what the future amount would actually be worth in current purchasing power.
What is the difference between beginning and end-of-period contributions?
A beginning-of-period contribution is added before interest is applied, so it earns one extra period of growth, producing a slightly higher final balance than an end-of-period contribution of the same amount.
Is this financial advice?
No. The calculator is an estimation tool that projects growth based on the figures you enter. Actual returns vary, and it does not account for taxes or fees.
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