± and ∓ contain the same two signs in opposite orders, but they’re separate Unicode characters and they aren’t always used the same way.
± is U+00B1 PLUS-MINUS SIGN.
∓ is U+2213 MINUS-OR-PLUS SIGN, often called the minus-plus sign.
You’ll see ± much more often on its own. ∓ is especially useful when a formula needs two sign choices to move in opposite directions.
± vs ∓ at a Glance
| Symbol | Code point | Unicode name | Typical use |
|---|---|---|---|
| ± | U+00B1 | PLUS-MINUS SIGN | Alternative plus/minus cases, uncertainty, tolerance, or another context-defined quantity |
| ∓ | U+2213 | MINUS-OR-PLUS SIGN | Often paired with ± when the second choice should reverse the first |
Both belong to the broader family of math symbols, but the surrounding notation determines what the two choices actually mean.
What Does ± Mean?
The plus-minus sign represents a plus-or-minus choice.
For example:
x = 5 ± 2
can compactly represent:
x = 5 + 2
and:
x = 5 − 2
so the two resulting values are 7 and 3.
Why Is ± Used in the Quadratic Formula?
The quadratic formula contains:
−b ± √(b² − 4ac)
because a quadratic equation can produce two solutions: one from the plus choice and one from the minus choice.
Here, ± lets one formula represent both cases at once.
What Does ∓ Mean?
∓ reverses the visual order: minus above, plus below.
Its most familiar use is alongside ± when two choices need to stay opposite.
For example:
a ± b ∓ c
is conventionally read as the paired cases:
a + b − c
and:
a − b + c
The upper choices go together, and the lower choices go together. That pairing is a mathematical notation convention, not behavior built into the Unicode characters themselves.
Why Not Write ± Twice?
If you write:
a ± b ± c
the relationship between the two sign choices may be unclear unless the author defines it.
In some contexts the signs may be intended to vary independently, which could produce four combinations. Writing:
a ± b ∓ c
is a common way to show that the second sign should take the opposite choice from the first.
Does ± Always Represent Two Exact Values?
No.
In algebra, ± often represents two discrete alternatives. In measurements, engineering specifications, or scientific reporting, it can describe uncertainty or tolerance instead.
For example:
10.0 ± 0.2
might describe an uncertainty, permitted tolerance, or another defined interval around 10.0.
The exact interpretation has to come from the field or document. The ± symbol by itself doesn’t tell you whether 0.2 is a standard deviation, measurement uncertainty, tolerance limit, or something else.
Does ± Mean “Approximately Equal”?
No.
± attaches a plus/minus quantity to a value or expression. It isn’t an equality relation.
Compare:
π ≈ 3.14
with:
3.14 ± 0.01
The first uses ≈ to express approximation. The second uses ± to attach a plus/minus quantity.
If you’re trying to separate the different approximation signs, ≈ vs ≅ vs ≃: Similar-Looking Equality Symbols Explained covers that family of symbols.
Is ∓ Just a Flipped Version of ±?
Visually, yes. Technically, no.
They have separate code points:
- U+00B1 → ± PLUS-MINUS SIGN;
- U+2213 → ∓ MINUS-OR-PLUS SIGN.
They’re separate characters, not font variants of one another.
Which One Should You Use?
Use ± when the notation calls for a plus-or-minus choice, uncertainty, tolerance, or another defined plus/minus quantity.
Use ∓ when you specifically need the minus-or-plus character—most often as the opposite partner of ± in paired formulas.
When a formula uses the conventional ±/∓ pairing, read the upper choices together and the lower choices together unless the source explicitly defines another convention.