Compound Interest Calculator

Calculate compound growth with contributions, withdrawals, inflation, and fees. Compare scenarios, view yearly breakdowns, and solve for the rate or savings needed to hit your goal.

Investment Details

Currency

Initial Investment

$0 $1M

Please enter a valid value

Annual Interest / Return Rate

0% 20%

Please enter a valid value

Compound Frequency

Years

0 50

Please enter a valid value

Months

0 11

Please enter a valid value

Regular Contributions

Contribution Amount

$0 $20k

Please enter a valid value

Contribution Frequency

Contribution Timing

Beginning of period End of period

Annual Contribution Increase

0% 20%

Please enter a valid value

Withdrawal Amount

$0 $20k

Please enter a valid value

Withdrawal Frequency

Withdrawal Timing

Beginning of period End of period

Annual Withdrawal Increase

0% 20%

Please enter a valid value

Inflation Rate

0% 10%

Please enter a valid value

Annual Account / Investment Fee

0% 3%

Please enter a valid value

Estimated Results

Future Value

$12,834

Total Contributions$0.00

Total Interest / Growth$2,834

Total Withdrawals−$0.00

Net Contributions$10,000

Initial Investment$10,000

EAR: 5.12%

Total Growth: 28.34%

Inflation-Adj: —

Growth Over Time

Account Value Total Contributions Inflation-Adjusted

Where the Final Balance Comes From

Your money: — Compound growth: —

Breakdown

Year	Start Balance	Contributions	Interest	Withdrawals	End Balance

Month	Start Balance	Contributions	Interest	Withdrawals	End Balance

Scenario Comparisons

Rate Sensitivity

How different annual rates affect your final balance.

Rate	Future Value	Total Growth
3.00%	$11,616	16.16%
4.00%	$12,210	22.10%
5.00%	$12,834	28.34%
6.00%	$13,489	34.89%
7.00%	$14,176	41.76%

Time Sensitivity

How your balance grows over different time horizons.

Period	Future Value	Total Growth
1 year	$10,512	5.12%
3 years	$11,615	16.15%
5 years	$12,834	28.34%
10 years	$16,470	64.70%
15 years	$21,137	111.37%
20 years	$27,126	171.26%
30 years	$44,677	346.77%

Effect of Regular Contributions

Compare your result with and without regular contributions.

Scenario	Future Value	Difference
Without regular contributions	$12,834	+$0.00
With current contributions	$12,834	+$0.00

Reverse Calculator

Work backward from a goal to find what you need.

Required Contribution

To reach $100,000 in 10 years at 7.00%:

$461.64/mo

Required regular contribution

Required Rate

To reach $100,000 in 10 years with current contributions:

5.98%

Required annual return

Required Time

To reach $100,000 at 7.00% with current contributions:

9 yr 6 mo

Required investment period

How This Calculator Works

Compound interest is calculated by applying the periodic rate to the current balance, including previously earned interest.
Contributions are added at the chosen frequency and timing (beginning or end of period), then compounded going forward.
Withdrawals reduce the balance before interest is applied for that period.
Annual fees are deducted as a percentage of the year-end balance, reducing effective growth.
Inflation adjustment discounts the final nominal value to show equivalent purchasing power in today's dollars.
EAR (Effective Annual Rate) = (1 + r/n)ⁿ − 1, where r is the nominal rate and n is compounding periods per year.

This tool provides estimates for planning purposes. Actual investment returns, fees, and inflation may differ. It does not model taxes, transaction costs, or investment risk.

Formulas

Future Value (lump sum): FV = P × (1 + r/n)^(nt)
Future Value (with contributions): FV = P(1+r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)] × (1 + r/n × timing)
Effective Annual Rate: EAR = (1 + r/n)ⁿ − 1
Inflation-Adjusted Value: Real FV = FV / (1 + inflation)^t
Total Growth %: (FV − Total Contributions) / Total Contributions × 100

Frequently Asked Questions

Q: What is compound interest?

Compound interest is interest calculated on the initial principal plus all accumulated interest from previous periods. Unlike simple interest, you earn "interest on interest," causing growth to accelerate over time.

Q: How does contribution timing affect results?

Contributions made at the beginning of each period start earning interest immediately, while end-of-period contributions earn one less compounding cycle. Over long timeframes, this difference can be meaningful.

Q: What is the effective annual rate (EAR)?

The effective annual rate is the actual return after accounting for compounding frequency. For example, 5% compounded monthly has an EAR of approximately 5.12%.

Q: How does inflation affect my investment?

Inflation reduces purchasing power over time. The calculator shows both the nominal future value and an inflation-adjusted value representing what that money would be worth in today's dollars.

Q: What is the difference between nominal and inflation-adjusted value?

Nominal value is the raw dollar amount in the future. Inflation-adjusted value discounts that amount by the assumed inflation rate to show equivalent purchasing power in today's money.

Q: How do fees impact long-term growth?

Even a small annual fee compounds into a significant drag over decades. A 0.5% annual fee on an 8% return effectively reduces your growth rate to 7.5%.

Q: Can I calculate how much I need to save to reach a goal?

Yes. Use the reverse calculator to enter your target amount, timeframe, and expected return — the calculator will solve for the required regular contribution.

Q: What compounding frequencies are supported?

Daily, weekly, biweekly, monthly, quarterly, semiannually, and annually. More frequent compounding yields slightly higher returns due to the EAR effect.