Interest Calculator
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Simple Interest Calculator

Determine interest accrued on short-term deposits, promissory notes, and loans.

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Simple Interest Inputs

$100$250.0k$500.0k
%
0.1%12.5%25%
Total Simple Interest Earned
$1,500

Over 3 years at 5% annual interest

Principal

$10.0k

Total Maturity

$11.5k

Monthly Interest$41.67
Daily Accrual$1.37

Principal vs. Simple Interest

Maturity Value$11.5k
Compare With Compound Interest

How much more would compounding earn?

If this amount were compounded monthly at the exact same rate (5%) for 3 years, the final balance would reach $11,615, earning you an additional +$115.

Try Compound Calc
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📐 The Universal Simple Interest Formula

The basic equation taught in financial arithmetic is:

SI = (P × R × T) / 100
P = PrincipalThe original sum of money lent or invested.
R = Annual RateThe percentage interest charged per year.
T = TimeDuration in years (or months / 12, or days / 365).

Frequently Asked Questions

What is Simple Interest?▼

Simple interest is a quick and straightforward method of calculating interest charges on a loan or deposit. It is computed solely on the original principal amount without taking prior accrued interest into account.

What is the Simple Interest formula?▼

The formula is SI = (P × R × T) / 100, where P is the Principal amount, R is the Annual Interest Rate in percent, and T is the Time period in years. The total maturity amount is simply A = P + SI.

Where is Simple Interest used in the real world?▼

Simple interest is standard in short-term financial instruments such as Government Treasury Bills (T-Bills), Certificate of Deposits (CDs), short-term commercial promissory notes, automobile installment contracts, and peer-to-peer personal loans.

What is the key difference between Simple and Compound Interest?▼

In simple interest, your interest earnings remain constant every single period because they are calculated only on the initial principal. In compound interest, each period's interest is added back to the balance, allowing your money to earn interest on interest and grow exponentially over time.