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Disclaimer
This calculator provides estimates for informational purposes only and does not constitute financial, medical, legal, or tax advice. Always consult a qualified professional about your specific situation.
How This Calculator Works
Simple interest is interest that accrues only on the original amount you started with, never on
interest you’ve already earned. Enter a principal amount, an annual interest rate, and a time
period, and this calculator computes exactly how much interest accrues and the total amount at
the end.
This is different from the Compound Interest Calculator, where interest earned in one period gets
added to the balance and starts earning its own interest the next period. Simple interest is
genuinely used for some short-term loans, certain bonds and promissory notes, and is usually the
first way interest is taught in a math class before compounding is introduced.
The Formula
I=P×100r×t
where I is the interest earned, P is the principal, r is the annual interest
rate as a percent, and t is the time in years (a 6-month period is entered as 0.5). The
total amount at the end is simply P+I.
Worked Example
A $1,000 principal at a 5% annual rate for 3 years:
Interest: I=1,000×1005×3=$150.
Total amount: $1,000+$150=$1,150.
Because simple interest never compounds, doubling the time period exactly doubles the interest —
6 years at the same rate would earn exactly $300, not more.
Cómo funciona esta calculadora
El interés simple es el interés que se acumula únicamente sobre el monto original con el que
comenzaste, nunca sobre el interés que ya has ganado. Ingresa un monto principal, una tasa de
interés anual y un período de tiempo, y esta calculadora calcula exactamente cuánto interés se
acumula y el monto total al final.
Esto es diferente de la Calculadora de Interés Compuesto, donde el interés ganado en un período se
suma al saldo y comienza a generar su propio interés en el siguiente período. El interés simple se
usa genuinamente en algunos préstamos a corto plazo, ciertos bonos y pagarés, y suele ser la
primera forma en que se enseña el interés en una clase de matemáticas antes de introducir la
capitalización.
La fórmula
I=P×100r×t
donde I es el interés ganado, P es el principal, r es la tasa de interés
anual expresada como porcentaje, y t es el tiempo en años (un período de 6 meses se
ingresa como 0.5). El monto total al final es simplemente P+I.
Ejemplo resuelto
Un principal de $1,000 a una tasa anual del 5% durante 3 años:
Interés: I=1,000×1005×3=$150.
Monto total: $1,000+$150=$1,150.
Debido a que el interés simple nunca se capitaliza, duplicar el período de tiempo duplica
exactamente el interés — 6 años a la misma tasa generarían exactamente $300, no más.
What is the difference between simple and compound interest?
Simple interest accrues only on the original principal, so it grows by the same dollar amount every period. Compound interest adds each period's interest back into the balance, so future interest is earned on that interest too — which grows faster over time. Use the Compound Interest Calculator if your account or loan compounds.
How do I calculate simple interest?
Multiply the principal by the annual interest rate (as a decimal) by the time in years: Interest = Principal x Rate x Time. Add that to the principal for the total amount.
What real-world situations use simple interest?
Some short-term personal loans, certain bonds and promissory notes, and car loans in some cases use simple interest. Most savings accounts, credit cards, and mortgages compound instead — check your specific account or loan terms.
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