Compound interest calculator

A compound interest calculator for your next step

What can a compound interest calculator show you?

Wondering how much a little extra each month could add up to? Start with the compound interest calculator above. Enter what you have saved, choose a rate, and see how your balance could grow. Change one input in the compound interest calculator to explore a different approach. Results update as you type.

Choose the question you want to answer

This compound interest calculator brings three tasks together. Choose Grow savings to project a future balance, Savings goal to find a monthly deposit, or Withdrawals to explore how long your money could last. The compound interest calculator keeps each mode’s inputs while you switch between them.

What does compounding mean?

“Interest paid on principal and on accumulated interest.”

Compound interest is interest earned on both your original money and interest already added to the account. That is why a compound interest calculator can show an accelerating growth curve without any new deposits. You may see “compounding interest calculator” used interchangeably with “compound interest calculator.” Both describe the same idea.

Getting started with the compound interest calculator

What to enter in your compound interest calculator

Your starting balance is the amount available today. Enter future deposits separately to avoid counting them twice. Starting from zero is fine: a compound interest calculator can show how regular saving builds a balance from scratch. The currency setting in the compound interest calculator changes the symbols, not the amount or exchange rate.

Try a few interest rates

The example rate is a starting point, not a current bank offer or forecast. Try different rates in the compound interest calculator, keeping other inputs unchanged. At zero interest, the compound interest calculator shows what your deposits would achieve on their own.

Time and frequency in the compound interest calculator

Set a timeline that fits your plan

The compound interest calculator accepts years plus extra months, up to 100 years in total. Two years and six months means 30 months of growth. With a zero-length plan, the compound interest calculator applies no future payments, even with beginning-of-period timing.

Keep payment and compounding schedules separate

This compound interest calculator supports annual, quarterly, monthly, and daily compounding. Choose your payment schedule separately in the compound interest calculator. Daily compounding uses 365 periods per year; the monthly schedule uses an equivalent monthly growth factor that preserves the annual growth rate.

Monthly or yearly compounding: which should you choose?

Choose Monthly in the compound interest calculator for 12 compounding periods per year, or Annually for yearly compounding. At the same positive nominal annual rate, monthly compounding produces a slightly higher balance because interest has more opportunities to earn interest. Use the frequency specified for the account or scenario you are modeling.

Compare monthly and yearly results

With $1,000, no additional deposits, and a 10% nominal annual rate, the compound interest calculator projects $1,104.71 after one year with monthly compounding, versus $1,100.00 with yearly compounding. Monthly contributions are a separate choice: you can add money every month with either compounding setting. The chart uses equivalent monthly growth factors, so it does not represent an account’s actual interest-posting dates.

Why a compound interest calculator may differ from your statement

The compound interest calculator uses equal months rather than actual transaction dates. It does not track leap years, weekends, or daily account balances. A bank using daily balances and its own rounding rules may produce a slightly different result.

The formula behind the compound interest calculator

Start with a single deposit

Without additional payments, a compound interest calculator uses this formula. A is the ending balance, P the starting principal, r the nominal annual rate as a decimal, n the compounding periods per year, and t the number of years.

Try $1,000 over two years

Enter $1,000 in the compound interest calculator, set contributions to zero, and choose 10% annual interest compounded annually for two years. The compound interest calculator returns $1,210. Year one earns $100; year two earns $110. That extra $10 is interest on your interest.

Using the compound interest calculator with regular deposits

Every deposit gets its own time to grow

A deposit made today grows for longer than one made next year. The compound interest calculator accounts for that difference. For monthly end deposits, C is the deposit, M the number of months, and q the monthly growth factor. S adds up the growth factors for those deposits.

How does a compound interest calculator handle deposit timing?

Beginning-of-month deposits get an extra month of growth, so the compound interest calculator multiplies the contribution term by q. At 0% interest, S equals M. Annual end deposits occur after each full year; beginning deposits occur when each projected year starts.

A monthly savings example

Start with $10,000, add $100 at each month-end, and use 5% nominal interest compounded monthly for 10 years. The compound interest calculator gives $31,998.32: $22,000 paid in and $9,998.32 in interest. Keep these compound interest calculator settings when checking the result in Excel.

Choosing a rate in the compound interest calculator

Should you enter APY in a compound interest calculator?

In Grow savings, the compound interest calculator accepts a nominal annual rate or annual percentage yield (APY). APY already includes compounding, so the compound interest calculator disables the frequency setting. A 12% nominal rate compounded monthly produces about 12.68% annual growth; 12% APY means exactly 12% annual growth.

Allow for inflation

Open More options in the compound interest calculator to add an inflation assumption. The purchasing-power estimate divides your future balance by (1 + inflation)^years to express it in today's money. The compound interest calculator leaves your nominal balance unchanged and does not increase contributions with inflation.

Use the compound interest calculator for a savings goal

Work backward with the compound interest calculator

Enter your starting balance, target, and timeline in Savings goal. The compound interest calculator works backward, allowing for interest on your existing savings. To give you a usable payment, the compound interest calculator rounds up to the next cent and projects that actual deposit.

A goal you can check without a formula

With $1,000 saved and a $2,200 target, you need another $1,200. Over 12 months at 0% interest, that is $100 a month. The compound interest calculator shows no deposit needed when existing savings and projected interest already cover the goal.

Understand the target milestone

Savings goal uses nominal interest and monthly deposits. For beginning deposits, the formula's denominator becomes S × q. The compound interest calculator marks the first monthly balance that reaches the target, not an exact calendar date. A higher assumed return lowers the deposit mathematically, but does not guarantee that return.

A compound interest calculator with withdrawals

See what remains as you take money out

Choose Withdrawals for monthly or yearly payments. This compound interest calculator tracks your remaining balance, interest, and total actually withdrawn. The compound interest calculator limits each payment to the money available. If the balance runs out, the schedule records a shortfall instead of assuming you borrow the difference.

Understanding shortfalls in a compound interest calculator

Try $200, zero interest, and three month-end withdrawals of $100 in the compound interest calculator. The balance reaches zero after payment two; the first shortfall comes in month three. Start with $250 instead and the payments are $100, $100, and $50, leaving $50 unfunded.

Check when the money leaves

The compound interest calculator projects less interest when withdrawals happen earlier. With $1,000 at 12% nominal interest compounded monthly, two $100 end withdrawals leave $819.10; beginning withdrawals leave $817.09. The opening row shows the balance before any immediate withdrawal. Ending balance plus actual withdrawals equals starting balance plus interest.

Reading your compound interest calculator results

Explore the numbers on the chart

Drag across the compound interest calculator chart to see a month's balance, interest, and cumulative deposits or withdrawals. Your compound interest calculator readout stays inside the graph. On a phone, the live result bar helps you move between inputs and results. Keyboard controls include arrows, Home, End, Page Up, and Page Down.

Choose a compound interest calculator table view

The compound interest calculator table shows running totals, not individual payments. The yearly view includes your opening balance and any final partial year. The compound interest calculator retains full precision but displays cents. Subtracting displayed figures can occasionally produce a one-cent rounding difference.

Check the compound interest calculator in Excel

Use FV for a future balance

To reproduce the monthly savings example from the compound interest calculator, use this FV formula. It starts with $10,000, adds $100 at each month-end, and applies 5% nominal interest compounded monthly for 120 months. Excel and the compound interest calculator both return $31,998.32. Negative inputs represent money you pay in.

=FV(5%/12,120,-100,-10000,0)

Check your compound interest calculator month by month

Multiply the opening balance by one plus the monthly rate, then add the end deposit. For beginning deposits, add the money first. Carry full precision into the next row. Comparing rows with the compound interest calculator schedule helps identify timing or rate differences.

Use PMT for a target

The zero-interest goal example gives $100 per month in Excel too. Like the compound interest calculator, this formula rounds required deposits upward to cents. Some regional settings need semicolons instead of commas.

=MAX(0,ROUNDUP(-PMT(0,12,-1000,2200,0),2))

For other compounding frequencies, the monthly rate is (1+r/n)^(n/12)−1. With APY, use (1+APY)^(1/12)−1. Match the worksheet to your compound interest calculator settings before comparing results.

Save or share your compound interest calculator results

Keep a copy in the format you need

All three modes in the compound interest calculator offer a PNG image, full monthly CSV, share link, copied summary, and print view. Preview an image before downloading it, or choose CSV to work with the numbers in a spreadsheet. Your compound interest calculator exports include the assumptions behind the result.

Return to a plan or send it to someone else

A share link restores the selected mode and its inputs in the compound interest calculator. Anyone with the link can read those amounts and settings. You can use the compound interest calculator without an account. Switching modes keeps your entries during the visit; reloading resets entries that are not included in the link you open.

Common compound interest calculator questions

Why does another calculator give a different answer?

Check that the rate type, frequency, payment timing, and duration match. This compound interest calculator assumes equal months and a fixed rate. Banks may use actual dates, daily balances, or different rounding rules. Those differences can change the answer without either calculation being wrong.

What if an input is missing or out of range?

The compound interest calculator highlights the field and hides the previous result until it is valid again. Correct the entry or use Reset example in the compound interest calculator. If something still looks wrong, click the email icon and include your settings, without account numbers, passwords, or other sensitive details.

Can a compound interest calculator predict investment returns?

No. A compound interest calculator illustrates the rate you enter; it cannot predict markets. This tool does not model losses, changing rates, taxes, fees, or withdrawal penalties. Its withdrawal projection does not establish a safe retirement spending rate. Treat it as a way to explore assumptions, not a promise of income.