Simple interest never earns interest. Compound interest does. Using the wrong one misstates the balance.
One multiplies, one does not
Simple interest is principal times rate times time. Five thousand dollars at 5% for three years earns $750, and that $750 does not earn anything further. Compound interest adds the $750 to the base and the next period pays interest on $5,750.
Classroom notes and some short loans use the simple formula. Savings accounts, funds, and retirement balances do not. If you use simple interest for a ten-year investment you will understate the result. Pick the simple interest calculator only when the contract is actually simple.
Run the same question with your figures
Simple Interest and Compound Interest Are Not Neighbors points to the Simple Interest Calculator because the note is about interest that never earns interest of its own. The form on that page asks for Principal ($5,000.00), Annual rate (5%), Time in years (3). Its opening example produces Interest is $750.00. Use the article to see which piece of the payment, the tax, or the balance the heading is talking about. Use the calculator when you want the same relationship with your own inputs. The two pages are not copies of each other.
Simple Interest and Compound Interest Are Not Neighbors points to the Compound Interest Calculator because the note is about interest that starts earning interest of its own. The form on that page asks for Starting amount ($10,000.00), Contribution each period ($200.00), Annual interest rate (6%), Compounds per year (12), Years (10). Its opening example produces Future value is $50,969.84. Use the article to see which piece of the payment, the tax, or the balance the heading is talking about. Use the calculator when you want the same relationship with your own inputs. The two pages are not copies of each other.
How to read this note
Simple Interest and Compound Interest Are Not Neighbors is one question, not a plan for every account you own. The opening claim is this: Simple interest never earns interest. Compound interest does. Using the wrong one misstates the balance. The sections above stay on that claim. They use a worked figure so the relationship is visible. A worked figure is not a prediction that your loan, your fund, or your tax year will match it.
Read the headings in order. One multiplies, one does not. If a sentence names a calculator, that link is the place to change the inputs. If a sentence names a limit, the limit is the one published for the year written on the page, which is 2026 where this desk cites a retirement or tax figure.
A senior reading of a finance page looks for three things. The formula should match the labels. The example should be reproducible on the calculator. The page should say what it leaves out. This note tries to do those three. It does not tell you to borrow, to sell, to contribute the maximum, or to file a return from the illustration.
What the note leaves out
Simple Interest and Compound Interest Are Not Neighbors ignores facts it does not mention. Fees, state tax, a credit score, an employer match you have not typed, and a market that refuses to pay a flat rate are all outside the paragraph. When one of those facts is the actual question, open the calculator that asks for it or read the disclaimer before you move money.
Published 25 Oct 2026. If a public figure in the note is later revised by the IRS, a lender, or a data source, the calculator page and the methodology are the places this desk updates. The note does not store what you type, and it is not a message from a broker or a tax preparer.
Before you treat the example as yours
Simple Interest and Compound Interest Are Not Neighbors uses a specific illustration so the relationship is easy to see. The category is Investing. The tools sitting next to the note are Simple Interest Calculator, Compound Interest Calculator. Open one of them, replace the example, and press Calculate if the decision in front of you depends on your balance, your rate, or your income. The article does not update itself when those facts change.
A careful reading checks three matches. The heading should be the question you have. The worked number should use inputs you can point to. The omitted items, named above, should be irrelevant or added back in a field. If any of the three fails, do not stretch the conclusion. Simple interest never earns interest. Compound interest does. Using the wrong one misstates the balance.
Keep the note and the calculator apart in your notes. The note explains why the pieces move. The calculator shows how far they move once you type them. Publishing date 25 Oct 2026 is the version of the explanation you are reading. Public limits can change after that date, and the methodology is where this desk records the figures it is willing to stand behind.
FAQs
Is a bond coupon simple interest?
The coupon is a set payment. The price of the bond is a present-value problem. Use the bond calculator when you care what the bond is worth at a given yield.
What is Simple Interest and Compound Interest Are Not Neighbors actually deciding?
Simple interest never earns interest. Compound interest does. Using the wrong one misstates the balance.
Where do I put my own numbers?
Open Simple Interest Calculator or Compound Interest Calculator. The article’s example is already explained. The calculator is the place to change the fields and press Calculate.
Does the example include every fee and tax?
Only the pieces the note names. Anything missing from the example is missing from the result. Add it in the matching field or treat the figure as incomplete.
Is this a recommendation?
No. Simple Interest and Compound Interest Are Not Neighbors shows a relationship so you can see it. It is not advice to buy, sell, borrow, or contribute. The disclaimer states that limit in one place.