Simple Interest Calculator

Calculate simple interest and total amount

Formula

Simple Interest = P × r × t. Total = P + I = P(1 + rt). P = Principal, r = annual rate (decimal), t = time in years.

Simple interest is calculated only on the original principal. It does not compound. Used for short-term loans and some fixed-income investments.

How to Calculate Manually

1
Select what you want to calculate
2
Enter the known values
3
Choose time unit (years, months, or days)
4
Calculator shows the result

Reference Table

Principal	Rate	Time	Interest	Total
$1,000	5%	1 yr	$50	$1,050
$1,000	5%	2 yr	$100	$1,100
$1,000	5%	5 yr	$250	$1,250
$1,000	10%	1 yr	$100	$1,100
$5,000	7%	3 yr	$1,050	$6,050
$10,000	4.5%	6 mo	$225	$10,225
$25,000	6%	90 days	$369.86	$25,369.86

Simple Interest Calculator: Calculate Interest, Principal, Rate, or Time

Simple interest is the most basic way to calculate interest on a loan or investment. Unlike compound interest, where you earn interest on your interest, simple interest is calculated only on the original principal amount. This makes it straightforward but less common for long-term investments...

Frequently Asked Questions

What's the difference between simple and compound interest? Simple interest: only on principal. Compound: on principal + accumulated interest. Simple = P × r × t. Compound = P(1+r)^t - P.: Simple interest: only on principal. Compound: on principal + accumulated interest. Simple = P × r × t. Compound = P(1+r)^t - P.
When is simple interest used? Short-term loans, some bonds, car loans (sometimes), treasury bills. Most savings accounts and mortgages use compound interest.: Short-term loans, some bonds, car loans (sometimes), treasury bills. Most savings accounts and mortgages use compound interest.
How do I calculate interest for partial years? Use time in years as decimal. 6 months = 0.5 years. 90 days = 90/365 = 0.2466 years. Calculator handles this automatically.: Use time in years as decimal. 6 months = 0.5 years. 90 days = 90/365 = 0.2466 years. Calculator handles this automatically.

Calculator

Formula

Formula

How to Calculate Manually

Reference Table

Simple Interest Calculator: Calculate Interest, Principal, Rate, or Time

Frequently Asked Questions

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