Plus-minus symbol ±

• Tolerances: a part machined to 2.000 ± 0.005 in can measure anywhere from 1.995 to 2.005 inches.
• Margins of error: a poll result of 48% with a margin of error of ± 3 percentage points means the true value is likely between 45% and 51%.
• Two solutions in math: the quadratic formula x = (−b ± √(b² − 4ac)) / 2a gives one answer with + and one with −. Likewise, if x² = 9, then x = ±3.
• Measurement uncertainty: in science, 9.81 ± 0.02 m/s² reports a value together with its uncertainty.

In casual writing, ± sometimes stands for “approximately,” as in “±50 guests.” That is understandable but imprecise; “about 50” is clearer.

• ∓ (minus-plus) appears together with ± when signs must flip in step: cos(a ± b) = cos a cos b ∓ sin a sin b. Read the upper signs together and the lower signs together.
• ⁺⁄₋ is an imitation built from three separate characters. Avoid it; it doesn’t behave like ± in search or for screen readers.
• +/- is the plain-text fallback, fine in code comments and quick emails.

With units, make it clear that the unit applies to both numbers. Following NIST guidance, write (20 ± 2) °C or 20 °C ± 2 °C rather than 20 ± 2 °C.

• Word: in an equation (Alt+=), type \pm and press space.
• Excel: ± is text, so a cell containing “5 ± 0.1” can’t be used in calculations. Keep the value and the tolerance in separate cells and add the sign only in a label.
• LaTeX: \pm for ±, \mp for ∓.
• iPhone and Android: there is no default key. Copy it from this page or set up a text replacement such as “plusmin” → ±.