Compound Interest Calculator
See how your money grows over time. Project the future value of a lump sum or regular monthly contributions, compare what you put in against the interest you earn, plan for retirement or solve the monthly amount needed to hit a goal — with growth charts, milestones and a printable report.
| Year | Total Contributions | Interest Earned | Ending Balance |
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How Compound Interest Works
Three steps from a starting amount to a full future value, interest total and growth timeline.
Choose a one-time lump sum, regular monthly contributions, a retirement plan, or solve the monthly amount needed to reach a target. Pick the scenario at the top.
Add your starting amount, expected annual return, time horizon and how often interest compounds — daily through annual. Optionally add a monthly contribution.
See the future value, interest earned and growth multiple, plus contribution-vs-interest charts, growth milestones and a full yearly table. Download a clean PDF report or copy the summary in one tap.
Investment Growth Projection
Model a lump sum, recurring contributions, a retirement runway, or reverse-engineer the monthly amount needed to hit a target.
Charts and milestones show exactly when compound interest overtakes your contributions and becomes the bigger half of your balance.
Everything runs in your browser — no sign-up, nothing sent anywhere, and results update the moment you press Calculate.
Export a polished, branded report with your summary, growth charts, contribution breakdown, milestones and a full yearly table.
Daily, monthly, quarterly, semi-annual or annual — with the effective annual yield shown so you can compare apples to apples.
Know the number you're aiming for? The Goal Target mode tells you exactly how much to invest each month to get there.
Related Finance Calculators
Round out your money plan with these companion tools.
Compound interest glossary
The key ideas behind long-term growth, in plain language.
Compound Interest Calculator for Investors and Savers
Compound interest is the engine behind almost every long-term financial goal. Instead of earning a return only on the money you put in, you also earn returns on the returns you have already collected. Over a few years the effect is modest, but over decades it compounds into the largest part of your balance — which is exactly what this calculator is built to show.
Start by entering an initial amount and an expected annual return, then choose how often it compounds. Daily, monthly, quarterly, semi-annual and annual compounding all produce a slightly different effective rate, so the tool reports your APY (annual percentage yield) alongside the nominal rate to keep comparisons fair. The result is your projected future value: what the investment is worth at the end of the period once every contribution and every compounding cycle is accounted for.
Adding a monthly contribution is where compounding really pays off. Investing a steady amount each month — the heart of long-term investing and retirement planning — means new money is constantly being put to work while your existing balance keeps growing. The contributions-versus-interest chart makes the turning point obvious: the year your accumulated interest finally overtakes the money you actually contributed.
For wealth building with a specific number in mind, the Goal Target mode works backwards. Tell it the amount you want to reach and your timeframe, and it solves for the monthly contribution required to get there. Whether you are sizing up an emergency fund, a house deposit or a retirement nest egg, you get a concrete monthly figure instead of a vague ambition.
If you are mapping out a complete financial plan, pair this with the rest of the suite: model a home loan with the Mortgage Calculator, price any borrowing with the Loan Calculator, set a concrete savings milestone with the Savings Goal Calculator, measure performance with the ROI Calculator, or clear high-interest balances faster with the Credit Card Payoff Calculator. Dedicated Retirement and Investment calculators round out the picture for longer-term planning.
Frequently Asked Questions
The short, practical answers investors ask most.
Compound interest is interest earned on both your original money and on the interest it has already earned. Because each period's growth is added to the balance before the next period is calculated, your money grows on an ever-larger base and accelerates over time. Simple interest, by contrast, is paid only on the original principal — which is why $10,000 at 7% grows to about $76,000 over 30 years with compounding, versus just $31,000 with simple interest.
More frequent compounding (daily or monthly) produces a slightly higher effective return than annual compounding for the same nominal rate, and the gap widens with higher rates and longer horizons. In practice the difference between monthly and daily is tiny. This calculator lets you choose daily, monthly, quarterly, semi-annual or annual, and shows the effective annual yield so you can compare options fairly.
Because returns compound, your earliest contributions have the most time to grow, and the interest-on-interest effect snowballs in the later years. Investing the same amount for 30 years instead of 20 can more than double the final value. That is why starting early usually matters more than investing larger amounts later — time is the single most powerful lever in the formula.
The Rule of 72 is a quick mental shortcut: divide 72 by your annual return percentage to estimate how many years it takes your money to double. At an 8% return money doubles in roughly 72 ÷ 8 = 9 years; at 6% it takes about 12 years. It is an approximation that works best for rates between about 4% and 12%, and it is a handy sanity check against the calculator's exact figures.
It depends on your target, your timeframe and your expected return. Use the Goal Target tab: enter the amount you want to reach, your current savings and an expected return, and the calculator solves for the required monthly contribution to get there by your chosen date. As a rough guide, investing $500/month at 7% for 30 years grows to over $600,000.
Reinvested returns generate their own returns, so over long horizons the interest-on-interest often becomes the majority of your balance — frequently far more than the money you actually contributed. Consistent contributions, a reasonable return and a long time horizon are the three levers that turn modest savings into substantial wealth. The yearly table on this page shows exactly when interest overtakes your contributions.