Summarize this article:
Last updated on August 26, 2025
999 in binary is written as 1111100111 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 999 in binary systems.
The process of converting 999 from decimal to binary involves dividing the number 999 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 999 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 999 by 2 until getting 0 as the quotient is 1111100111. 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 999. 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 1111100111 in binary is indeed 999 in the decimal number system.
999 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 999 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
Since 512 is less than 999, we stop at 29 = 512.
Step 2 - Identify the largest power of 2: In the previous step, we stopped at 29 = 512.
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, 999.
Since 29 is the number we are looking for, write 1 in the 29 place.
Now the value of 29, which is 512, is subtracted from 999. 999 - 512 = 487.
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, 487.
So, the next largest power of 2 is 28, which is less than or equal to 487.
Now, we have to write 1 in the 28 places.
And then subtract 256 from 487. 487 - 256 = 231.
Step 4 - Repeat the process for remaining values: Identify the next largest power of 2 that fits into 231, which is 27 = 128. 231 - 128 = 103.
Then, 26 = 64 fits into 103. 103 - 64 = 39.
Then, 25 = 32 fits into 39. 39 - 32 = 7.
Then, 22 = 4 fits into 7. 7 - 4 = 3.
Then, 21 = 2 fits into 3. 3 - 2 = 1.
Finally, 20 = 1 fits into 1. 1 - 1 = 0.
Now, by substituting the values, we get: 1 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 0 in the 23 place 1 in the 22 place 1 in the 21 place 1 in the 20 place
Step 5 - Write the values in reverse order: We now write the numbers upside down to represent 999 in binary. Therefore, 1111100111 is 999 in binary.
Grouping Method: In this method, we divide the number 999 by 2.
Let us see the step-by-step conversion.
Step 1 - Divide the given number 999 by 2. 999 / 2 = 499.
Here, 499 is the quotient and 1 is the remainder.
Step 2 - Divide the previous quotient (499) by 2. 499 / 2 = 249.
Here, the quotient is 249 and the remainder is 1.
Step 3 - Repeat the previous steps until the quotient is 0. 249 / 2 = 124, remainder 1. 124 / 2 = 62, remainder 0. 62 / 2 = 31, remainder 0. 31 / 2 = 15, remainder 1. 15 / 2 = 7, remainder 1. 7 / 2 = 3, remainder 1. 3 / 2 = 1, remainder 1. 1 / 2 = 0, remainder 1.
Step 4 - Write down the remainders from bottom to top.
Therefore, 999 (decimal) = 1111100111 (binary).
There are certain rules to follow when converting any number to binary. Some of them are mentioned below:
Rule 1: Place Value Method 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 999. Since the answer is 29, write 1 next to this power of 2. Subtract the value (512) from 999, so 999 - 512 = 487. Find the largest power of 2 less than or equal to 487. The answer is 28. So, write 1 next to this power. Continue this process until the remainder is 0. Final conversion will be 1111100111.
Rule 2: Division by 2 Method 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, 999 is divided by 2 to get 499 as the quotient and 1 as the remainder. Now, 499 is divided by 2. Here, we will get 249 as the quotient and 1 as the remainder. Dividing 249 by 2, we get 124 as the quotient and 1 as the remainder. Continue this process until the quotient is 0. Now, we write the remainders upside down to get the binary equivalent of 999, 1111100111.
Rule 3: Representation Method 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., 29, 28, 27, etc. Find the largest power that fits into 999. 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.
Rule 4: Limitation Rule 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 999, we use 1s and 0s for appropriate powers of 2.
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 999. Memorize to speed up conversions: We can memorize the binary forms for numbers with common patterns.
Recognize the patterns: There is a peculiar pattern when converting numbers from decimal to binary. Even and odd rule: Whenever a number is even, its binary form will end in 0.
For example, 10 is even, and its binary form is 1010. Here, the binary of 10 ends in 0. If the number is odd, then its binary equivalent will end in 1.
For example, the binary of 17 (an odd number) is 10001. 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 999 from decimal to binary using the place value method.
1111100111
29 is the largest power of 2, which is less than or equal to 999. So place 1 next to 29. Subtracting 512 from 999, we get 487. So the next largest power would be 28. So place another 1 next to 28. Continue this process until all values are covered. By using this method, we can find the binary form of 999.
Convert 999 from decimal to binary using the division by 2 method.
1111100111
Divide 999 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 999 to binary using the representation method.
1111100111
Break the number 999 into powers of 2 and find the largest powers of 2. We get 29. So 1 is placed next to 29. Next, 999 - 512 = 487. Now, the largest power of 2 is 28. Once again, 1 is placed next to 28. Continue this process until all values are covered. By following this method, we get the binary value of 999 as 1111100111.
How is 999 written in decimal, octal, and binary form?
Decimal form - 999 Octal - 1747 Binary - 1111100111
The decimal system is also called the base 10 system. In this system, 999 is written as 999 only. We have already seen how 999 is written as 1111100111 in binary. The octal system is base 8. To convert 999 to octal, divide by 8 and write the remainders in reverse order. 999 / 8 = 124 remainder 7. 124 / 8 = 15 remainder 4. 15 / 8 = 1 remainder 7. 1 / 8 = 0 remainder 1. Thus, the octal equivalent of 999 is 1747.
Express 999 - 500 in binary.
111101011
999 - 500 = 499. So, we need to write 499 in binary. Start by dividing 499 by 2. We get 249 as the quotient and 1 as the remainder. Next, divide 249 by 2. Now we get 124 as the quotient and 1 as the remainder. Continue this process until the quotient is 0. Write the remainders from bottom to top to get 111101011 (binary of 499).
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.