# How to calculate simple and compound interest

Mathematics is an integral part of programming. If you cannot solve simple problems in this area, you will have a much harder time than you need to.

Fortunately, learning how to do it is not too difficult. In this article, you will learn how to calculate simple and compound interest using Python, C ++, and JavaScript.

How do you calculate simple interest?

Simple interest is a method of calculating the amount of interest charged on a principal amount at a given rate and for a given period of time. You can calculate simple interest using the following formula:

`Simple Interest = (P x R x T)/100 `

Where,

P = Principle Amount

R = Rate

T = Time

### The problem statement

we give you **principal amount**, **interest rate**, and **time**. You need to calculate and print the simple interest for the given values. **Example**: Either principle = 1000, rate = 7 and timePeriod = 2. Simple interest = (principle * rate * timePeriod) / 100 = (1000 * 7 * 2) / 100 = 140. Thus, the output is 140.

### The C ++ program to calculate simple interest

Here is the C ++ program to calculate simple interest:

`// C++ program to calculate simple interest`

// for given principle amount, time, and rate of interest.

#include

using namespace std;

// Function to calculate simple interest

float calculateSimpleInterest(float principle, float rate, float timePeriod)

{

return (principle * rate * timePeriod) / 100;

}int main()

{

float principle1 = 1000;

float rate1 = 7;

float timePeriod1 = 2;

cout << "Test case: 1" << endl;

cout << "Principle amount: " << principle1 << endl;

cout << "Rate of interest: " << rate1 << endl;

cout << "Time period: " << timePeriod1 << endl;

cout << "Simple Interest: " << calculateSimpleInterest(principle1, rate1, timePeriod1) << endl;

float principle2 = 5000;

float rate2 = 5;

float timePeriod2 = 1;

cout << "Test case: 2" << endl;

cout << "Principle amount: " << principle2 << endl;

cout << "Rate of interest: " << rate2 << endl;

cout << "Time period: " << timePeriod2 << endl;

cout << "Simple Interest: " << calculateSimpleInterest(principle2, rate2, timePeriod2) << endl;

float principle3 = 5800;

float rate3 = 4;

float timePeriod3 = 6;

cout << "Test case: 3" << endl;

cout << "Principle amount: " << principle3 << endl;

cout << "Rate of interest: " << rate3 << endl;

cout << "Time period: " << timePeriod3 << endl;

cout << "Simple Interest: " << calculateSimpleInterest(principle3, rate3, timePeriod3) << endl;

return 0;

}

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Simple Interest: 140

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Simple Interest: 250

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Simple Interest: 1392

### The Python program to calculate simple interest

Below is the Python program to calculate simple interest:

`# Python program to calculate simple interest`

# for given principle amount, time, and rate of interest.

# Function to calculate simple interest

def calculateSimpleInterest(principle, rate, timePeriod):

return (principle * rate * timePeriod) / 100principle1 = 1000

rate1 = 7

timePeriod1 = 2

print("Test case: 1")

print("Principle amount:", principle1)

print("Rate of interest:", rate1)

print("Time period:", timePeriod1)

print("Simple Interest:", calculateSimpleInterest(principle1, rate1, timePeriod1))

principle2 = 5000

rate2 = 5

timePeriod2 = 1

print("Test case: 2")

print("Principle amount:", principle2)

print("Rate of interest:", rate2)

print("Time period:", timePeriod2)

print("Simple Interest:", calculateSimpleInterest(principle2, rate2, timePeriod2))

principle3 = 5800

rate3 = 4

timePeriod3 = 6

print("Test case: 3")

print("Principle amount:", principle3)

print("Rate of interest:", rate3)

print("Time period:", timePeriod3)

print("Simple Interest:", calculateSimpleInterest(principle3, rate3, timePeriod3))

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Simple Interest: 140.0

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Simple Interest: 250.0

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Simple Interest: 1392.0

### The JavaScript program to calculate simple interest

Below is the JavaScript program to calculate simple interest:

`// JavaScript program to calculate simple interest`

// for given principle amount, time, and rate of interest.

// Function to calculate simple interest

function calculateSimpleInterest(principle, rate, timePeriod) {

return (principle * rate * timePeriod) / 100;

}

var principle1 = 1000;

var rate1 = 7;

var timePeriod1 = 2;

document.write("Test case: 1" + "

");

document.write("Principle amount: " + principle1 + "

");

document.write("Rate of interest: " + rate1 + "

");

document.write("Time period: " + timePeriod1 + "

");

document.write("Simple Interest: " + calculateSimpleInterest(principle1, rate1, timePeriod1) + "

");

var principle2 = 5000;

var rate2 = 5;

var timePeriod2 = 1;

document.write("Test case: 2" + "

");

document.write("Principle amount: " + principle2 + "

");

document.write("Rate of interest: " + rate2 + "

");

document.write("Time period: " + timePeriod2 + "

");

document.write("Simple Interest: " + calculateSimpleInterest(principle2, rate2, timePeriod2) + "

");

var principle3 = 5800;

var rate3 = 4;

var timePeriod3 = 6;

document.write("Test case: 3" + "

");

document.write("Principle amount: " + principle3 + "

");

document.write("Rate of interest: " + rate3 + "

");

document.write("Time period: " + timePeriod3 + "

");

document.write("Simple Interest: " + calculateSimpleInterest(principle3, rate3, timePeriod3) + "

");

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Simple Interest: 140

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Simple Interest: 250

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Simple Interest: 1392

How to calculate compound interest

Compound interest is the addition of interest to the principal amount. In other words, it’s interest over interest. You can calculate compound interest using the following formula:

` Amount= P(1 + R/100)T`

Compound Interest = Amount – P

Where,

P = Principle Amount

R = Rate

T = Time

### The problem statement

we give you **principal amount**, **interest rate**, and **time**. You need to calculate and print the compound interest for the given values. **Example**: Either principle = 1000, rate = 7 and timePeriod = 2. Amount = P (1 + R / 100) T = 1144.9 Compound interest = Amount – Principal amount = 1144.9 – 1000 = 144.9 Thus, the output is 144.9.

### The C ++ program to calculate compound interest

Below is the C ++ program to calculate compound interest:

`// C++ program to calculate compound interest`

// for given principle amount, time, and rate of interest.

#include

using namespace std;

// Function to calculate compound interest

float calculateCompoundInterest(float principle, float rate, float timePeriod)

{

double amount = principle * (pow((1 + rate / 100), timePeriod));

return amount - principle;

}

int main()

{

float principle1 = 1000;

float rate1 = 7;

float timePeriod1 = 2;

cout << "Test case: 1" << endl;

cout << "Principle amount: " << principle1 << endl;

cout << "Rate of interest: " << rate1 << endl;

cout << "Time period: " << timePeriod1 << endl;

cout << "Compound Interest: " << calculateCompoundInterest(principle1, rate1, timePeriod1) << endl;

float principle2 = 5000;

float rate2 = 5;

float timePeriod2 = 1;

cout << "Test case: 2" << endl;

cout << "Principle amount: " << principle2 << endl;

cout << "Rate of interest: " << rate2 << endl;

cout << "Time period: " << timePeriod2 << endl;

cout << "Compound Interest: " << calculateCompoundInterest(principle2, rate2, timePeriod2) << endl;

float principle3 = 5800;

float rate3 = 4;

float timePeriod3 = 6;

cout << "Test case: 3" << endl;

cout << "Principle amount: " << principle3 << endl;

cout << "Rate of interest: " << rate3 << endl;

cout << "Time period: " << timePeriod3 << endl;

cout << "Compound Interest: " << calculateCompoundInterest(principle3, rate3, timePeriod3) << endl;

return 0;

}

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Compound Interest: 144.9

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Compound Interest: 250

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Compound Interest: 1538.85

### The Python program to calculate compound interest

Below is the Python program to calculate compound interest:

`# Python program to calculate compound interest`

# for given principle amount, time, and rate of interest.

# Function to calculate compound interest

def calculateCompoundInterest(principle, rate, timePeriod):

amount = principle * (pow((1 + rate / 100), timePeriod))

return amount - principle

principle1 = 1000

rate1 = 7

timePeriod1 = 2

print("Test case: 1")

print("Principle amount:", principle1)

print("Rate of interest:", rate1)

print("Time period:", timePeriod1)

print("Compound Interest:", calculateCompoundInterest(principle1, rate1, timePeriod1))

principle2 = 5000

rate2 = 5

timePeriod2 = 1

print("Test case: 2")

print("Principle amount:", principle2)

print("Rate of interest:", rate2)

print("Time period:", timePeriod2)

print("Compound Interest:", calculateCompoundInterest(principle2, rate2, timePeriod2))

principle3 = 5800

rate3 = 4

timePeriod3 = 6

print("Test case: 3")

print("Principle amount:", principle3)

print("Rate of interest:", rate3)

print("Time period:", timePeriod3)

print("Compound Interest:", calculateCompoundInterest(principle3, rate3, timePeriod3))

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Compound Interest: 144.9000000000001

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Compound Interest: 250.0

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Compound Interest: 1538.8503072768026

### The JavaScript program to calculate compound interest

Below is the JavaScript program to calculate compound interest:

`// JavaScript program to calculate compound interest`

// for given principle amount, time, and rate of interest.// Function to calculate compound interest

function calculateCompoundInterest(principle, rate, timePeriod) {

var amount = principle * (Math.pow((1 + rate / 100), timePeriod));

return amount - principle;

}

var principle1 = 1000;

var rate1 = 7;

var timePeriod1 = 2;

document.write("Test case: 1" + "

");

document.write("Principle amount: " + principle1 + "

");

document.write("Rate of interest: " + rate1 + "

");

document.write("Time period: " + timePeriod1 + "

");

document.write("Compound Interest: " + calculateCompoundInterest(principle1, rate1, timePeriod1) + "

");

var principle2 = 5000;

var rate2 = 5;

var timePeriod2 = 1;

document.write("Test case: 2" + "

");

document.write("Principle amount: " + principle2 + "

");

document.write("Rate of interest: " + rate2 + "

");

document.write("Time period: " + timePeriod2 + "

");

document.write("Compound Interest: " + calculateCompoundInterest(principle2, rate2, timePeriod2) + "

");

var principle3 = 5800;

var rate3 = 4;

var timePeriod3 = 6;

document.write("Test case: 3" + "

");

document.write("Principle amount: " + principle3 + "

");

document.write("Rate of interest: " + rate3 + "

");

document.write("Time period: " + timePeriod3 + "

");

document.write("Compound Interest: " + calculateCompoundInterest(principle3, rate3, timePeriod3) + "

");

Go out:

`Test case: 1`

Principle amount: 1000

Rate of interest: 7

Time period: 2

Compound Interest: 144.9000000000001

Test case: 2

Principle amount: 5000

Rate of interest: 5

Time period: 1

Compound Interest: 250

Test case: 3

Principle amount: 5800

Rate of interest: 4

Time period: 6

Compound Interest: 1538.8503072768008

Learn to code for free: start with simple and compound interest

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