Investing calculator

Compound Interest Calculator

Explore the effect of rate, time, compounding frequency, and optional contributions on a balance. The breakdown separates money added from estimated interest earned.

Your assumptions

Adjust the numbers

Results update as you type. Starting values are examples—replace them with your own numbers before making a decision.

Saved scenarios

0 of 3 saved

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Your estimate

What the numbers say

Estimated ending balance$55,291

After 10 years at the rate and frequencies entered.

Total contributed$40,000

Estimated interest$15,291

Effective annual rate5.1%

Ending balance breakdown

Starting balance$10,000

Recurring contributions$30,000

Estimated interest$15,291

Scenario range

Compare growth assumptions over time

Conservative, base, and optimistic are labels for the rates you entered—not forecasts or probability ranges. Constant returns smooth out real-world volatility.

Conservative (3%)Base (5%)Optimistic (7%)

Start

$10,000

Year 2

$16,793

$17,346

$17,918

Year 3

$20,346

$21,303

$22,312

Year 5

$27,778

$29,835

$32,074

Year 7

$35,669

$39,263

$43,300

Year 8

$39,796

$44,341

$49,528

Year 10

$48,429

$55,291

$63,368

Year-by-year scenario balances
Point	Conservative	Base	Optimistic
Start	$10,000	$10,000	$10,000
Year 1	$13,346	$13,581	$13,821
Year 2	$16,793	$17,346	$17,918
Year 3	$20,346	$21,303	$22,312
Year 4	$24,006	$25,463	$27,023
Year 5	$27,778	$29,835	$32,074
Year 6	$31,664	$34,431	$37,491
Year 7	$35,669	$39,263	$43,300
Year 8	$39,796	$44,341	$49,528
Year 9	$44,048	$49,679	$56,206
Year 10	$48,429	$55,291	$63,368

Preparing detailed analysis…

Estimate only. Actual costs and outcomes vary. Verify important decisions with current quotes and qualified professionals.

How it works

What this estimate calculates

The starting principal follows the compound-interest formula A = P(1 + r/n)^(nt). Recurring contributions are compounded from their assumed deposit dates at the same periodic rate, and the ending balance is separated into principal contributed and estimated interest.

Assumptions to keep in mind

The entered annual rate stays constant and interest is credited at the selected frequency.
Recurring contributions are equal and made at the displayed point in each contribution period.
Taxes, fees, withdrawals, rate changes, and inflation are not included unless entered elsewhere in the tool.

Reviewed references

Sources behind this calculator

Last reviewed: August 21, 2026. These references support the concepts and context; their publishers do not review or endorse TrueCost.

Compound Interest Calculator (opens in a new tab)Investor.gov, U.S. Securities and Exchange Commission
Using principal, contributions, years, rate, variance, and compounding frequency as projection inputs.
Growing Money: Compound Interest (opens in a new tab)Federal Reserve Education
Combining a starting balance with recurring contributions and compound growth.

Read the full methodology

Questions people ask

What does compounding frequency change?

It controls how often earned interest is added to the balance. With the same stated annual rate, more frequent compounding can produce a slightly different effective return.

What is the difference between interest and contributions?

Contributions are the money you add. Interest is the modeled growth generated by the balance under the rate and compounding assumptions.

Is the result guaranteed?

No. It is a mathematical projection. Savings rates can change, and investment returns fluctuate and may be negative.

Use the result as a starting point

Try a conservative scenario and an optimistic one. If the decision only works under one narrow set of assumptions, that is useful information. For a purchase, loan, tax, or investment decision, confirm the final figures with current documents and an appropriately qualified professional.

Read the full financial disclaimer