Last updated on 22 August 2025
8421 in binary is written as 1000011110101 because the binary system uses only two digits, 0 and 1, to represent numbers. This number system is used widely in computer systems. In this topic, we are going to learn about binary systems and how to convert 8421 to binary.
The process of converting 8421 from decimal to binary involves dividing the number 8421 by 2. Here, it is divided by 2 because the binary number system uses only 2 digits (0 and 1). The quotient becomes the dividend in the next step, and the process continues until the quotient becomes 0.
This is a commonly used method to convert 8421 to binary. In the last step, the remainder is noted down from bottom to top, and that becomes the converted value. For example, the remainders noted down after dividing 8421 by 2 until getting 0 as the quotient is 1000011110101. Remember, the remainders here have been written upside down.
In the table shown below, the first column shows the binary digits (1 and 0) as 1000011110101. The second column represents the place values of each digit, and the third column is the value calculation, where the binary digits are multiplied by their corresponding place values.
The results of the third column can be added to cross-check if 1000011110101 in binary is indeed 8421 in the decimal number system.
8421 can be converted easily from decimal to binary. The methods mentioned below will help us convert the number. Let’s see how it is done.
Expansion Method: Let us see the step-by-step process of converting 8421 using the expansion method.
Step 1 - Figure out the place values: In the binary system, each place value is a power of 2. Therefore, in the first step, we will ascertain the powers of 2.
20 = 1
21 = 2
22 = 4
23 = 8
24 = 16
25 = 32
26 = 64
27 = 128
28 = 256
29 = 512
210 = 1024
211 = 2048
212 = 4096
213 = 8192
Since 8192 is less than 8421, we include 213, which is 8192.
Step 2 - Identify the largest power of 2: In the previous step, we identified 213 = 8192 as the largest power of 2 less than or equal to 8421. Write 1 in the 213 place and subtract this value from 8421: 8421 - 8192 = 229.
Step 3 - Identify the next largest power of 2: Now, find the largest power of 2 that fits into 229, which is 27 = 128. Write 1 in the 27 place. Subtract 128 from the result of the previous step: 229 - 128 = 101.
Step 4 - Continue the process: Repeat the process for 101. 26 = 64 fits into 101, so write 1 in the 26 place. 101 - 64 = 37. 25 = 32 fits into 37, so write 1 in the 25 place. 37 - 32 = 5. 22 = 4 fits into 5, so write 1 in the 22 place. 5 - 4 = 1. 20 = 1 fits into 1, so write 1 in the 20 place. 1 - 1 = 0.
Step 5 - Identify the unused place values: Fill 0s in the places where no power of 2 was used. Now, by substituting the values, we get: 1 in the 213 place 0 in the 212 place 0 in the 211 place 0 in the 210 place 0 in the 29 place 1 in the 28 place 1 in the 27 place 1 in the 26 place 1 in the 25 place 0 in the 24 place 1 in the 23 place 0 in the 22 place 1 in the 21 place 1 in the 20 place Therefore, 1000011110101 is 8421 in binary.
Grouping Method: In this method, we divide the number 8421 by 2. Let us see the step-by-step conversion.
Step 1 - Divide 8421 by 2. 8421 / 2 = 4210 remainder 1.
Step 2 - Divide the previous quotient (4210) by 2. 4210 / 2 = 2105 remainder 0.
Step 3 - Repeat the previous step. 2105 / 2 = 1052 remainder 1.
Step 4 - Repeat the previous step. 1052 / 2 = 526 remainder 0.
Step 5 - Repeat the previous step. 526 / 2 = 263 remainder 0.
Step 6 - Repeat the previous step. 263 / 2 = 131 remainder 1.
Step 7 - Repeat the previous step. 131 / 2 = 65 remainder 1.
Step 8 - Repeat the previous step. 65 / 2 = 32 remainder 1.
Step 9 - Repeat the previous step. 32 / 2 = 16 remainder 0.
Step 10 - Repeat the previous step. 16 / 2 = 8 remainder 0.
Step 11 - Repeat the previous step. 8 / 2 = 4 remainder 0.
Step 12 - Repeat the previous step. 4 / 2 = 2 remainder 0.
Step 13 - Repeat the previous step. 2 / 2 = 1 remainder 0.
Step 14 - Repeat the previous step. 1 / 2 = 0 remainder 1. Write down the remainders from bottom to top.
Therefore, 8421 (decimal) = 1000011110101 (binary).
There are certain rules to follow when converting any number to binary. Some of them are mentioned below:
This is one of the most commonly used rules to convert any number to binary. The place value method is the same as the expansion method, where we need to find the largest power of 2. Let’s see a brief step-by-step explanation to understand the first rule. Find the largest power of 2 less than or equal to 8421. Since the answer is 213, write 1 next to this power of 2. Subtract the value (8192) from 8421. So, 8421 - 8192 = 229. Find the largest power of 2 less than or equal to 229. The answer is 27. So, write 1 next to this power. Now, 229 - 128 = 101. Continue the process until you reach 0. Final conversion will be 1000011110101.
The division by 2 method is the same as the grouping method. A brief step-by-step explanation is given below for better understanding. First, 8421 is divided by 2 to get 4210 as the quotient and 1 as the remainder. Now, 4210 is divided by 2. Here, we will get 2105 as the quotient and 0 as the remainder. Dividing 2105 by 2, we get 1052 as the quotient and 1 as the remainder. Continue the division process until the quotient becomes 0. Now, write the remainders upside down to get the binary equivalent of 8421, 1000011110101.
This rule also involves breaking the number into powers of 2. Identify the powers of 2 and write them down in decreasing order, i.e., 213, 212, 211, etc. Find the largest power that fits into 8421. Repeat the process and allocate 1s and 0s to the suitable powers of 2. Combine the digits (0 and 1) to get the binary result.
The limitation of the binary system is that only 0s and 1s can be used to represent numbers. The system doesn’t use any other digits other than 0 and 1. This is a base 2 number system, where the binary places represent powers of 2. So, every digit is either a 0 or a 1.
Learning a few tips and tricks is a great way to solve any mathematical problems easily. Let us take a look at some tips and tricks for binary numbers up to 8421.
Here, let us take a look at some of the most commonly made mistakes while converting numbers to binary.
Convert 8421 from decimal to binary using the place value method.
1000011110101
213 is the largest power of 2, which is less than or equal to 8421.
So place 1 next to 213.
Subtracting 8192 from 8421, we get 229.
The next largest power would be 27.
So place another 1 next to 27.
Continue this process until you reach 0.
By using this method, we can find the binary form of 8421.
Convert 8421 from decimal to binary using the division by 2 method.
1000011110101
Divide 8421 by 2. In the next step, the quotient becomes the new dividend.
Continue the process until the quotient becomes 0.
Now, write the remainders upside down to get the final result.
Convert 8421 to binary using the representation method.
1000011110101
Break the number 8421 into powers of 2 and find the largest powers of 2.
We get 213.
So 1 is placed next to 213.
Next, 8421 - 8192 = 229.
Now, the largest power of 2 is 27.
Once again, 1 is placed next to 27.
Continue this process until you reach 0, filling in with zeros for unused powers of 2.
By following this method, we get the binary value of 8421 as 1000011110101.
How is 8421 written in decimal, octal, and binary form?
Decimal form - 8421 Octal - 20215 Binary - 1000011110101
The decimal system is also called the base 10 system. In this system, 8421 is written as 8421 only.
We have already seen how 8421 is written as 1000011110101 in binary.
So, let us focus on the octal system, which is base 8.
To convert 8421 to octal, we need to divide 8421 by 8 and continue the process.
Write the remainders in reverse order to get 20215 as the octal equivalent of 8421.
Express 8421 - 7 in binary.
1000011110100
8421 - 7 = 8414
So, we need to write 8414 in binary.
Start by dividing 8414 by 2.
In each step, write down the remainder and continue dividing the quotient by 2 until the quotient becomes 0.
Finally, write down the remainders from bottom to top to get 1000011110100 (binary of 8414).
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
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