Guide · Compound interest

How compound interest works

Educational guide · Updated · About 8 min read

Compound interest means growth builds on earlier growth when interest is added to the balance and itself earns interest later.

Core idea

With discrete compounding: A = P(1 + r/n)^(n·t). Continuous compounding uses A = P·e^(r·t).

Sample

$10,000.00 · 5% · 10 years · monthly → about $16,470.09. Open sample

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Frequently asked questions

What is compound interest in plain words?

You earn interest on the original amount and on interest already added, so the balance can grow faster than simple interest at the same rate.

How much is $10,000 at 5% for 10 years (sample)?

About $16,470.09 with monthly compounding under Nestfigure’s model.

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Estimate growth with free math

Principal, rate, years, compounding, optional deposits.

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Sources linked above include U.S. government materials (for example CFPB, FDIC, NCUA, BLS, IRS) where noted. Sample math uses only labeled Nestfigure assumptions—not bank quotes, job offers, or personalized advice. Last reviewed: August 9, 2026.

YMYL notice: This site is for education only. It is not financial, tax, or investment advice. Nestfigure is not a bank, credit union, broker, investment adviser, or fiduciary. Product terms, rates, and penalties vary—always read your institution’s disclosures before acting. Calculator results are mathematical estimates, not bank quotes.