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Simple Interest Calculator

Calculate simple interest (I = P·r·t) and the final balance on a principal, where interest accrues only on the original amount.

Interest earned
$150.00
Final balance
$1,150.00

How it works

Simple interest is I = P × r × t, where P is the principal, r is the annual rate as a decimal, and t is the term in years. The final balance is just P + I. Interest is always calculated on the original principal only — it never compounds on previously earned interest, which is what makes it 'simple' compared to compound interest.

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