Last updated on August 18th, 2025
66 in binary is written as 1000010 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 66 in binary systems.
The process of converting 66 from decimal to binary involves dividing the number 66 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 66 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 66 by 2 until getting 0 as the quotient is 1000010. 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 1000010. 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 1000010 in binary is indeed 66 in the decimal number system.
66 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 66 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 less than 66, we stop at 26 = 64.
Step 2 - Identify the largest power of 2: In the previous step, we stopped at 26 = 64. 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, 66. Since 26 is the number we are looking for, write 1 in the 26 place. Now the value of 26, which is 64, is subtracted from 66. 66 - 64 = 2.
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, 2. So, the next largest power of 2 is 21, which is equal to 2. Now, we have to write 1 in the 21 place. And then subtract 2 from 2. 2 - 2 = 0. We need to stop the process here since the remainder is 0.
Step 4 - Identify the unused place values: In step 2 and step 3, we wrote 1 in the 2^6 and 2^1 places. Now, we can just write 0s in the remaining places, which are 20, 22, 23, 24, and 25.
Now, by substituting the values, we get, 0 in the 20 place 1 in the 21 place 0 in the 22 place 0 in the 23 place 0 in the 24 place 0 in the 2^5 place 1 in the 26 place
Step 5 - Write the values in reverse order: We now write the numbers upside down to represent 66 in binary. Therefore, 1000010 is 66 in binary. Grouping Method: In this method, we divide the number 66 by 2. Let us see the step-by-step conversion.
Step 1 - Divide the given number 66 by 2. 66 / 2 = 33. Here, 33 is the quotient and 0 is the remainder.
Step 2 - Divide the previous quotient (33) by 2. 33 / 2 = 16. Here, the quotient is 16 and the remainder is 1.
Step 3 - Repeat the previous step. 16 / 2 = 8. Now, the quotient is 8, and 0 is the remainder.
Step 4 - Repeat the previous step. 8 / 2 = 4. Here, the quotient is 4, and 0 is the remainder.
Step 5 - Repeat the previous step. 4 / 2 = 2. Here, the quotient is 2, and 0 is the remainder.
Step 6 - Repeat the previous step. 2 / 2 = 1. Here, the quotient is 1, and 0 is the remainder.
Step 7 - Repeat the previous step. 1 / 2 = 0.
Here, the remainder is 1. And we stop the division here because the quotient is 0.
Step 8 - Write down the remainders from bottom to top. Therefore, 66 (decimal) = 1000010 (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 66. Since the answer is 2^6, write 1 next to this power of 2. Subtract the value (64) from 66. So, 66 - 64 = 2. Find the largest power of 2 less than or equal to 2. The answer is 21. So, write 1 next to this power. Now, 2 - 2 = 0. Since there is no remainder, we can write 0 next to the remaining powers (20, 22, 23, 24, and 25). Final conversion will be 1000010.
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, 66 is divided by 2 to get 33 as the quotient and 0 as the remainder. Now, 33 is divided by 2. Here, we will get 16 as the quotient and 1 as the remainder. Dividing 16 by 2, we get 8 as the quotient and 0 as the remainder. Continuing this process, we divide 8 by 2 to get 4 as the quotient and 0 as the remainder. Divide 4 by 2 to get 2 as the quotient and 0 as the remainder. Divide 2 by 2 to get 1 as the quotient and 0 as the remainder. Finally, divide 1 by 2 to get 0 as the quotient and 1 as the remainder. We stop the division once the quotient becomes 0. Now, we write the remainders upside down to get the binary equivalent of 66, 1000010.
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., 26, 25, 24, 23, 22, 21, and 20. Find the largest power that fits into 66. 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 66, we use 0s for 25, 24, 23, 22, and 20 and 1s for 26 and 21.
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 66.
Memorize to speed up conversions: We can memorize the binary forms for numbers 1 to 10, and then practice with larger numbers.
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, 66 is even and its binary form is 1000010. Here, the binary of 66 ends in 0. If the number is odd, then its binary equivalent will end in 1. For example, the binary of 67 (an odd number) is 1000011. 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 66 from decimal to binary using the place value method.
1000010
26 is the largest power of 2, which is less than or equal to 66. So place 1 next to 26. Subtracting 64 from 66, we get 2. So the next largest power would be 21. So place another 1 next to 21. Now, subtracting 2 from 2, we get 0.
Now, we just place 0s in the remaining powers of 2, which are 20, 22, 23, 24, and 25. By using this method, we can find the binary form of 66.
Convert 66 from decimal to binary using the division by 2 method.
1000010
Divide 66 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 66 to binary using the representation method.
1000010
Break the number 66 into powers of 2 and find the largest powers of 2. We get 2^6. So 1 is placed next to 26. Next, 66 - 64 = 2. Now, the largest power of 2 is 21. Once again, 1 is placed next to 21.
Now, 2 - 2 = 0. After getting 0, fill in with zeros for unused powers of 2. By following this method, we get the binary value of 66 as 1000010.
How is 66 written in decimal, octal, and binary form?
Decimal form - 66 Octal - 102 Binary - 1000010
The decimal system is also called the base 10 system. In this system, 66 is written as 66 only. We have already seen how 66 is written as 1000010 in binary.
So, let us focus on the octal system, which is base 8. To convert 66 to octal, we need to divide 66 by 8. So 66 / 8 = 8 with 2 as the remainder.
In the next step, divide the quotient from the previous step (8) by 8. So 8 / 8 = 1 with 0 as the remainder. The division process stops here because the quotient is now 0. Here, 0, 2, and 1 are the remainders, and they have to be written in reverse order. So, 102 is the octal equivalent of 66.
Express 66 - 10 in binary.
101110
66 - 10 = 56 So, we need to write 56 in binary. Start by dividing 56 by 2. We get 28 as the quotient and 0 as the remainder.
Next, divide 28 by 2. Now we get 14 as the quotient and 0 as the remainder. Divide 14 by 2 to get 7 as the quotient and 0 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 111000 (binary of 56).
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.