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Last updated on August 20, 2025
61 in binary is written as 111101 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 61 binary systems.
The process of converting 61 from decimal to binary involves dividing the number 61 by 2. Here, it is getting 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 61 to binary. In the last step, the remainder is noted down bottom side up, and that becomes the converted value.
For example, the remainders noted down after dividing 61 by 2 until getting 0 as the quotient is 111101. 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 111101. 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 111101 in binary is indeed 61 in the decimal number system.
61 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 61 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 Since 64 is greater than 61, we stop at 25 = 32.
Step 2 - Identify the largest power of 2: In the previous step, we stopped at 25 = 32. This is because, in this step, we have to identify the largest power of 2, which is less than or equal to the given number, 61. Since 25 is the number we are looking for, write 1 in the 25 place. Now the value of 2^5, which is 32, is subtracted from 61. 61 - 32 = 29.
Step 3 - Identify the next largest power of 2: In this step, we need to find the largest power of 2 that fits into the result of the previous step, 29. So, the next largest power of 2 is 24 = 16. Now, we have to write 1 in the 24 place. And then subtract 16 from 29. 29 - 16 = 13.
Step 4 - Continue identifying the next largest powers: The next largest power of 2 for 13 is 2^3 = 8. Write 1 in the 23 place. 13 - 8 = 5. Now, the next largest power for 5 is 22 = 4. Write 1 in the 2 place. 5 - 4 = 1. For 1, the largest power of 2 is 2^0 = 1. Write 1 in the 2^0 place. 1 - 1 = 0. We need to stop the process here since the remainder is 0.
Step 5 - Identify the unused place values: In step 2 to step 4, we wrote 1 in the 2^5, 2^4, 2^3, 2^2, and 2^0 places. Now, we can just write 0s in the remaining place, which is 2^1. Now, by substituting the values, we get, 1 in the 2^0 place 0 in the 2^1 place 1 in the 2^2 place 1 in the 2^3 place 1 in the 2^4 place 1 in the 2^5 place
Step 6 - Write the values in reverse order: We now write the numbers upside down to represent 61 in binary. Therefore, 111101 is 61 in binary.
Grouping Method: In this method, we divide the number 61 by 2. Let us see the step-by-step conversion.
Step 1 - Divide the given number 61 by 2. 61 / 2 = 30. Here, 30 is the quotient and 1 is the remainder.
Step 2 - Divide the previous quotient (30) by 2. 30 / 2 = 15. Here, the quotient is 15 and the remainder is 0.
Step 3 - Repeat the previous step. 15 / 2 = 7. Now, the quotient is 7, and 1 is the remainder.
Step 4 - Repeat the previous step. 7 / 2 = 3. Here, the quotient is 3, and 1 is the remainder.
Step 5 - Repeat the previous step. 3 / 2 = 1. Here, the quotient is 1 and 1 is the remainder.
Step 6 - Repeat the previous step. 1 / 2 = 0. Here, the remainder is 1. And we stop the division here because the quotient is 0.
Step 7 - Write down the remainders from bottom to top. Therefore, 61 (decimal) = 111101 (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 61. Since the answer is 2^5, write 1 next to this power of 2. Subtract the value (32) from 61. So, 61 - 32 = 29. Find the largest power of 2 less than or equal to 29. The answer is 2^4. So, write 1 next to this power. Now, 29 - 16 = 13. Find the largest power of 2 less than or equal to 13. The answer is 2^3. So, write 1 next to this power. Now, 13 - 8 = 5. Find the largest power of 2 less than or equal to 5. The answer is 2^2. So, write 1 next to this power. Now, 5 - 4 = 1. Find the largest power of 2 less than or equal to 1. The answer is 2^0. So, write 1 next to this power. Now, 1 - 1 = 0. Since there is no remainder, we can write 0 next to the remaining power (2^1). Final conversion will be 111101.
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, 61 is divided by 2 to get 30 as the quotient and 1 as the remainder. Now, 30 is divided by 2. Here, we will get 15 as the quotient and 0 as the remainder. Dividing 15 by 2, we get 7 as the quotient and 1 as the remainder. Dividing 7 by 2, we get 3 as the quotient and 1 as the remainder. Dividing 3 by 2, we get 1 as the quotient and 1 as the remainder. Divide 1 by 2 to get 1 as the remainder and 0 as the quotient. We stop the division once the quotient becomes 0. Now, we write the remainders upside down to get the binary equivalent of 61, 111101.
This rule also involves breaking the number into powers of 2. Identify the powers of 2 and write it down in decreasing order, i.e., 2^5, 2^4, 2^3, 2^2, 2^1, and 2^0. Find the largest power that fits into 61. 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. To convert 61, we use 0 for 2^1 and 1s for 2^5, 2^4, 2^3, 2^2, and 2^0.
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 61.
Memorize to speed up conversions: We can memorize the binary forms for numbers 1 to 61. 1 → 1, 2 → 10, 3 → 11, 4 → 100, 5 → 101, 6 → 110, 7 → 111, 8 → 1000, 9 → 1001, 10 → 1010, ..., 61 → 111101.
Recognize the patterns: There is a peculiar pattern when converting numbers from decimal to binary. 1 → 1 1 + 1 = 2 → 10 2 + 2 = 4 → 100 4 + 4 = 8 → 1000 8 + 8 = 16 → 10000 16 + 16 = 32 → 100000 32 + 32 = 64 → 1000000 …and so on. This is also called the double and add rule.
Even and odd rule: Whenever a number is even, its binary form will end in 0. For example, 60 is even, and its binary form is 111100. Here, the binary of 60 ends in 0. If the number is odd, then its binary equivalent will end in 1. For example, the binary of 61 (an odd number) is 111101. As you can see, the last digit here is 1.
Cross-verify the answers: Once the conversion is done, we can cross-verify the answers by converting the number back to the decimal form. This will eliminate any unforeseen errors in conversion.
Practice by using tables: Writing the decimal numbers and their binary equivalents on a table will help us remember the conversions.
Here, let us take a look at some of the most commonly made mistakes while converting numbers to binary.
Convert 61 from decimal to binary using the place value method.
111101
2^5 is the largest power of 2, which is less than or equal to 61. So place 1 next to 2^5. Subtracting 32 from 61, we get 29. The next largest power would be 2^4. So place another 1 next to 2^4. Now, subtracting 16 from 29, we get 13. The next largest power is 2^3. Place 1 next to 2^3. Subtracting 8 from 13 gives 5. The next largest power is 2^2. Place 1 next to 2^2. Subtracting 4 from 5 gives 1. Finally, place 1 next to 2^0. By using this method, we can find the binary form of 61.
Convert 61 from decimal to binary using the division by 2 method.
111101
Divide 61 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 61 to binary using the representation method.
111101
Break the number 61 into powers of 2 and find the largest powers of 2. We get 2^5. So 1 is placed next to 2^5. Next, 61 - 32 = 29. Now, the largest power of 2 is 2^4. Once again, 1 is placed next to 2^4. Continue this process for 2^3, 2^2, and 2^0. After getting 0, fill in with zeros for unused powers of 2. By following this method, we get the binary value of 61 as 111101.
How is 61 written in decimal, octal, and binary form?
Decimal form - 61 Octal - 75 Binary - 111101
The decimal system is also called the base 10 system. In this system, 61 is written as 61 only. We have already seen how 61 is written as 111101 in binary. So, let us focus on the octal system, which is base 8. To convert 61 to octal, we need to divide 61 by 8. So 61 / 8 = 7 with 5 as the remainder. The division process stops here because the quotient is now 7, which is less than 8. So, 75 is the octal equivalent of 61.
Express 61 - 31 in binary.
11110
61 - 31 = 30 So, we need to write 30 in binary. Start by dividing 30 by 2. We get 15 as the quotient and 0 as the remainder. Next, divide 15 by 2. Now we get 7 as the quotient and 1 as the remainder. Divide 7 by 2 to get 3 as the quotient and 1 as the remainder. Divide 3 by 2 to get 1 as the quotient and 1 as the remainder. Finally, divide 1 by 2 to get 0 as the quotient and 1 as the remainder. Now write the remainders from bottom to top to get 11110 (binary of 30).
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.
: She loves to read number jokes and games.