Calculators for you Contact Us

1s and 2s Complement Calculator

Use our 1's and 2s Complement Calculator, a free online conversion tool to calculate 2's complement and 1s complement for binary values

1's Complement (One's Complement)

In mathematics, negative numbers in any base are represented by prefixing them with a − sign (negative sign). However, in computer hardware, numbers are represented in binary without any extra symbols, requiring a method of encoding the minus sign. In computing, ones's complement is one of the method to represent the negative numbers. However, 2s complement is dominant today. 1s complement could not have widespread use because of issues like negative zero, end-around borrow, etc.

1s complement calculation

The 1s complement of a number is found by changing all ones to zeros and all zeros to ones. This is called as taking complement or 1's complement.


1's complement of "0111" is "1000"

2's Complement (Two's Complement)

Ones complement has no special usage for negative integers. Two's complement makes sense because it can be used in natural addition and subtraction arithmetic without any need to change the bits. Providing that no overflow occurs, the sign bit of the result is just the right value.

Primary Advantage of two's complement is that the it has one value for zero while one's complement has 2 values for zero each for "Positive" zero & "Negative" zero. Another advantage is that two's complement doesn't require carry values.

Another method of representing signed numbers is two's complement. Most computers use this method to represent negative numbers. This method can be more effective when performing mathematical operations like adding and subtracting. For instance, the free two's complement calculator also determines the 2s complement of any given binary numeral with detailed calculations shown.

2s complement calculation

The 2s complement of binary number is obtained by adding 1 to the Least Significant Bit (LSB) of ones complement of the number.

2s complement = 1s complement + 1


2's complement of "0111" is "1001"

1s and 2s Complement Questions and Answers

Question.1: What does it mean to complement a binary number?
Answer.1: To complement a binary number means to change all the 1's to 0's and all the 0's to 1's.

Question.2: In 1's complement, what do all the negative numbers have in common?
Answer.2: In 1's complement, all the negative numbers begin with a 1.

Question.3: How do we write 0 using 4-bit 1's complement representation?
Answer.3: In 1's complement we have two ways of writing 0. Both 00002 and 11112 are correct.

Question.4: What extra step do we take when we form the 2's complement of a negative binary number?
Answer.4: The extra step we take is adding 1 to our complemented number. A good way to remember this is to compare the names of the representation schemes. 2's complement exceeds 1's complement by 1, so we always add 1 to our complemented numbers when using 2's complement.

Question.5: In 2's complement, what do all the positive numbers have in common?
Answer.5: In 2's complement, all the positive numbers begin with a 0.

Question.6: State Advantage of 2's complement over 1's complement?
Answer.6: In 2's complement we have only one way to represent 0. This simplifies our representation scheme.

Spreading Knowledge Across the World

USA - United States of America  Canada  United Kingdom  Australia  New Zealand  South America  Brazil  Portugal  Netherland  South Africa  Ethiopia  Zambia  Singapore  Malaysia  India  China  UAE - Saudi Arabia  Qatar  Oman  Kuwait  Bahrain  Dubai  Israil  England  Scotland  Norway  Ireland  Denmark  France  Spain  Poland  and  many more....