Enter any number to automatically compute its opposite (flip the sign)
Result
Opposite of the original number
Step-by-Step Derivation
Opposite Number Formula
Opposite of a = -a
The opposite of a number is found by flipping its sign. A positive number becomes negative, a negative becomes positive, and the opposite of 0 is 0.
⚠Note: This tool supports integers, decimals, negative numbers, and scientific notation. It automatically flips the sign. The sum of any number and its opposite is always 0.
What Is an Opposite Number?
Opposite numbers are one of the most fundamental concepts in algebra: two numbers that have the same absolute value but different signs are opposites of each other.
Sign Flip
The essence of an opposite number is a sign flip: positive ↔ negative, while 0 stays the same.
Same Absolute Value
Two opposite numbers have exactly the same absolute value, differing only in sign.
Sum Is Zero
Any number plus its opposite equals 0: a + (-a) = 0.
Geometric Meaning
On a number line, opposite numbers are symmetric about the origin (0).
💡 Teaching Example: The opposite of 5 is -5, the opposite of -3.8 is 3.8, and the opposite of 0 is 0.
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