Bash Script to Convert Celsius to Fahrenheit

Use the formula F = (C * 9/5) + 32 in a Bash script like fahrenheit=$(echo "scale=2; ($celsius * 9/5) + 32" | bc) to convert Celsius to Fahrenheit.

Examples

Input0

Output32.00

Input25

Output77.00

Input-40

Output-40.00

How to Think About It

To convert Celsius to Fahrenheit, multiply the Celsius value by 9, divide by 5, then add 32. In Bash, since it does not support floating-point math natively, use the external tool bc to perform the calculation and keep decimal precision.

Algorithm

1

Get the Celsius temperature input from the user or variable

2

Calculate Fahrenheit using the formula: multiply Celsius by 9, divide by 5, then add 32

3

Use a tool like <code>bc</code> to handle decimal math in Bash

4

Print the Fahrenheit result

Code

bash

#!/bin/bash
read -p "Enter temperature in Celsius: " celsius
fahrenheit=$(echo "scale=2; ($celsius * 9/5) + 32" | bc)
echo "$celsius Celsius is $fahrenheit Fahrenheit"

Output

Enter temperature in Celsius: 25
25 Celsius is 77.00 Fahrenheit

Dry Run

Let's trace converting 25 Celsius to Fahrenheit through the code

1

Input Celsius

User enters 25

2

Calculate Fahrenheit

Calculate (25 * 9/5) + 32 = 45 + 32 = 77.00 using bc

3

Print Result

Output: '25 Celsius is 77.00 Fahrenheit'

Step	Celsius	Calculation	Fahrenheit
1	25	25 * 9/5 + 32	77.00

Why This Works

Step 1: Formula for Conversion

The formula F = (C * 9/5) + 32 converts Celsius to Fahrenheit by scaling and shifting the temperature.

Step 2: Using bc for Decimal Math

Bash cannot do floating-point math directly, so bc is used to calculate with decimals and precision.

Step 3: Reading Input and Output

The script reads Celsius from the user, calculates Fahrenheit, then prints the result clearly.

Alternative Approaches

Using awk for calculation

bash

#!/bin/bash
read -p "Enter Celsius: " celsius
fahrenheit=$(awk "BEGIN {print ($celsius * 9/5) + 32}")
echo "$celsius Celsius is $fahrenheit Fahrenheit"

Awk can also do floating-point math without needing bc, making the script simpler.

Using integer math approximation

bash

#!/bin/bash
read -p "Enter Celsius: " celsius
fahrenheit=$(( (celsius * 9 / 5) + 32 ))
echo "$celsius Celsius is $fahrenheit Fahrenheit"

This uses integer math only, so it loses decimal precision but is simpler and faster.

Complexity: O(1) time, O(1) space

Time Complexity

The script performs a fixed number of arithmetic operations and input/output steps, so it runs in constant time.

Space Complexity

It uses a few variables and no extra data structures, so space usage is constant.

Which Approach is Fastest?

Integer math is fastest but less precise; using bc or awk adds slight overhead but supports decimals accurately.

Approach	Time	Space	Best For
Using bc	O(1)	O(1)	Accurate decimal math
Using awk	O(1)	O(1)	Simpler decimal math without bc
Integer math	O(1)	O(1)	Fast, approximate results