Superscript and Subscript Characters

Superscript and subscript characters are raised or lowered glyphs used extensively in mathematics, chemistry, phonetics, and general typography. Unicode provides a set of precomposed superscript and subscript characters that render as raised or lowered text without requiring any markup — no HTML <sup> or <sub> tags, no LaTeX commands, just plain text characters. This guide catalogs every Unicode superscript and subscript character, explains their limitations, and provides practical guidance for scientific writing, programming, and web development.

Why Precomposed Superscripts and Subscripts Exist

In digital text, there are three ways to render superscript or subscript text:

The Unicode approach is uniquely portable. A superscript ² is a single code point (U+00B2) that renders as a raised "2" in any context — terminal, plain text file, SMS, email subject line, filename, or database field. No markup engine is needed.

This portability comes at a cost: Unicode only provides superscript and subscript forms for a limited set of characters (primarily digits and a few letters). For arbitrary text, markup or font features are still necessary.

Superscript Characters

Superscript Digits

Note that ¹, ², and ³ are in the Latin-1 Supplement block (inherited from ISO 8859-1), while the rest are in the Superscripts and Subscripts block. This historical quirk means ², ³, and ¹ have broader legacy support.

Superscript Letters and Signs

Modifier Letters as Superscripts

The Spacing Modifier Letters block (U+02B0-U+02FF) and Phonetic Extensions blocks contain additional superscript letter forms used primarily in phonetics and linguistics:

These are linguistically important but serve a different purpose than the general superscript characters.

Subscript Characters

Subscript Digits

Subscript Letters and Signs

Practical Applications

Mathematics: Exponents and Indices

The most common use of superscripts is mathematical exponents:

x² + y² = z²           (Pythagorean theorem)
E = mc²                 (mass-energy equivalence)
aⁿ + bⁿ = cⁿ           (Fermat's Last Theorem)
x⁰ = 1                  (zero exponent rule)
2⁻¹ = ½                 (negative exponent)

Chemistry: Chemical Formulas

Chemical formulas use subscripts for atom counts and superscripts for charges:

H₂O                     (water)
CO₂                     (carbon dioxide)
C₆H₁₂O₆                (glucose)
Ca²⁺                    (calcium ion, charge 2+)
SO₄²⁻                   (sulfate ion, charge 2-)
Fe₂O₃                   (iron(III) oxide)

Ordinal Indicators

Some languages use superscripts for ordinal numbers:

1ˢᵗ  2ⁿᵈ  3ʳᵈ  4ᵗʰ     (English ordinals, informal)
Nᵒ                       (Numero sign, abbreviation)

Note: These informal "superscript ordinals" use modifier letters and are not standard Unicode practice. The feminine ordinal indicator (U+00AA, ª) and masculine ordinal indicator (U+00BA, º) are the proper characters for Romance language ordinals.

Building a Superscript/Subscript Converter in Python

Here is a utility that converts regular digits to their superscript or subscript equivalents:

SUPERSCRIPT_MAP = str.maketrans("0123456789+-=()", "⁰¹²³⁴⁵⁶⁷⁸⁹⁺⁻⁼⁽⁾")
SUBSCRIPT_MAP = str.maketrans("0123456789+-=()", "₀₁₂₃₄₅₆₇₈₉₊₋₌₍₎")

def to_superscript(text: str) -> str:
    return text.translate(SUPERSCRIPT_MAP)

def to_subscript(text: str) -> str:
    return text.translate(SUBSCRIPT_MAP)

# Usage
print(f"x{to_superscript('2')} + y{to_superscript('2')}")  # x² + y²
print(f"H{to_subscript('2')}O")                              # H₂O
print(f"a{to_superscript('(n+1)')}")                          # a⁽ⁿ⁺¹⁾

Limitations

Unicode superscripts and subscripts have important limitations:

For full control over superscript and subscript rendering, HTML/CSS markup remains the most reliable approach:

<!-- HTML approach: works with any character -->
<p>x<sup>n+1</sup> + y<sub>max</sub></p>

<!-- Unicode approach: limited to available characters -->
<p>x&#x207F;&#x207A;&#x00B9; + y&#x2098;&#x2090;&#x2093;</p>

Accessibility

Screen readers handle Unicode superscripts and subscripts inconsistently. Some readers announce ² as "superscript two", others as "squared", and some simply say "two". For scientific content where correct reading is critical, consider using MathML or ARIA labels:

<span aria-label="x squared">x²</span>
<span aria-label="H 2 O">H₂O</span>

Summary

Unicode provides precomposed superscript and subscript characters for all ten digits (0-9), several Latin letters, and basic mathematical operators. These characters are invaluable for plain-text environments where markup is unavailable, making it possible to write chemical formulas, mathematical expressions, and footnote markers in any text context. However, the character set is incomplete — only a subset of the Latin alphabet has super/subscript forms — so HTML/CSS markup or MathML remains necessary for arbitrary superscript and subscript content.