Degree and Temperature Symbols

The degree symbol (°) is one of the most frequently misused characters in Unicode. It is routinely confused with the superscript letter "o", the masculine ordinal indicator "º", the ring above combining diacritic, and the empty set symbol. This guide clarifies every degree-adjacent character in Unicode, covering their code points, correct usage, and how to type them.

Quick Copy-Paste Table

The Degree Sign: U+00B0

The degree sign (°, U+00B0) is the standard character for expressing:

• Temperature with a unit: 37°C, 98.6°F, 0°C
• Angles in geometry and navigation: 90°, 360°, bearing 045°
• Geographic coordinates: 48°51′N, 2°21′E
• Arc measurement in astronomy: Right Ascension 18h 29′ 45″

Spacing Rules

Spacing conventions for the degree sign vary by context:

The SI Brochure (the international standard for units) recommends a space between the number and the unit symbol, including °C. However, common practice — particularly in journalism and informal writing — omits the space. Check your style guide and be consistent.

Keyboard Shortcuts

℃ Degree Celsius: U+2103

Unicode includes a precomposed Degree Celsius character (℃, U+2103) as a single code point. This is a compatibility character — it exists for round-trip compatibility with legacy CJK encodings (particularly JIS X 0208) that encoded it as a single character.

Should you use U+2103 or °C?

The Unicode Standard explicitly recommends against using U+2103 in new text:

"The sequence °C (U+00B0 DEGREE SIGN + U+0043 LATIN CAPITAL LETTER C) is preferred over ℃ (U+2103 DEGREE CELSIUS)."

Use °C (two characters) in HTML, XML, web content, and code. Reserve U+2103 only when working with legacy CJK data or systems that require the single-codepoint form.

That said, the precomposed form exists and renders correctly in modern fonts. You may encounter it in Japanese, Chinese, or Korean text and should be prepared to handle it.

import unicodedata

# U+2103 normalises to °C under NFKC
nfkc = unicodedata.normalize("NFKC", "\u2103")
print(nfkc)        # °C (two characters)
print(len(nfkc))   # 2

℉ Degree Fahrenheit: U+2109

Identical situation to Celsius: U+2109 (℉) is a compatibility character, and the preferred representation is °F (U+00B0 + U+0046).

Fahrenheit remains the primary temperature scale in the United States, Belize, and a few other countries. When writing for an international audience, consider including both:

Water boils at 100°C (212°F) at sea level.

Kelvin: No Degree Symbol

The kelvin (K) is the SI base unit for thermodynamic temperature and — unlike Celsius and Fahrenheit — it is written without the degree sign and without a space between the number and K:

• Correct: 273.15 K, 0 K (absolute zero)
• Incorrect: 273.15°K, 273.15° K

This is because kelvin is an absolute scale, not a relative one. The SI Brochure is explicit: "The kelvin and its symbol, K, have been adopted…the degree sign is not used."

Look-Alike Characters: The Confusion Zone

Several characters look like the degree sign and cause persistent confusion:

Masculine Ordinal Indicator: º (U+00BA)

The masculine ordinal indicator (º) is used in Spanish, Portuguese, Italian, and other Romance languages to abbreviate ordinal numbers:

• 1º = primero (first, masculine)
• 2º = segundo (second, masculine)
• 10º andar = 10th floor

It looks like a superscript "o" but it is a distinct character with different Unicode properties. Do not use it for temperature or angles.

Feminine Ordinal Indicator: ª (U+00AA)

Used for feminine ordinal forms: - 1ª = primera (first, feminine) - 3ª edición = 3rd edition (feminine noun)

Ring Above: ˚ (U+02DA)

The ring above (˚, U+02DA) is a combining diacritic modifier letter used in phonetics and to form characters like Å (Angstrom sign). It is not a degree sign and should not be used as one. Unfortunately, it appears superficially identical to ° in many fonts.

How to tell them apart (developer view)

import unicodedata

chars = {
    "\u00B0": "degree sign",
    "\u00BA": "masculine ordinal indicator",
    "\u02DA": "ring above (modifier letter)",
    "\u2218": "ring operator",
    "\u25CB": "white circle",
}

for char, label in chars.items():
    name = unicodedata.name(char)
    cat  = unicodedata.category(char)
    print(f"{char}  U+{ord(char):04X}  {cat:3}  {name}  ({label})")

℧ Inverted Ohm (Mho): U+2127

The mho symbol (℧, U+2127) — an upside-down omega (Ω) — represents electrical conductance, the reciprocal of resistance. The unit is now officially called the siemens (S) in the SI system, making ℧ primarily a historical/legacy symbol.

You may encounter it in older electrical engineering texts. Its Unicode name is "INVERTED OHM SIGN."

Minutes and Seconds of Arc: ′ and ″

Geographic coordinates use prime (′) and double prime (″) for arc-minutes and arc-seconds — not apostrophes and quotation marks:

Correctly typeset coordinates:

The Eiffel Tower is at 48°51′29″N, 2°17′40″E

Scientific Writing Best Practices

Rule 1: Spell out units in text, abbreviate in tables and figures

"The sample was heated to 200 degrees Celsius." (prose) "T = 200°C" (table, equation)

Rule 2: Use the correct Unicode characters

Never use the letter "o" (superscript or otherwise) in place of the degree sign.

Rule 3: Kelvin gets no degree sign, ever

Even informal writing should respect this: "350 K" not "350°K."

Rule 4: Consistency in spacing

Pick a convention (no space vs. thin space before °C) and apply it throughout the document.

HTML Implementation

<!-- Correct temperature markup using microdata -->
<span itemprop="temperature">
  <span class="value">37</span><abbr class="unit" title="degrees Celsius">°C</abbr>
</span>

<!-- For screen reader accessibility, consider aria-label -->
<span aria-label="37 degrees Celsius">37°C</span>

<!-- Schema.org QuantitativeValue for structured data -->
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "QuantitativeValue",
  "value": 37,
  "unitCode": "CEL",
  "unitText": "°C"
}
</script>

CSS and Font Considerations

The degree sign is present in virtually every font at U+00B0. However, the precomposed ℃ (U+2103) and ℉ (U+2109) are only present in fonts with broad Unicode coverage (e.g., Noto Sans, Arial Unicode MS).

/* Ensure degree sign renders correctly in monospace contexts */
.temperature {
  font-variant-numeric: tabular-nums; /* Align temperature values in tables */
}

/* Superscript degree workaround for legacy browsers */
.degree-fallback::after {
  content: "\00B0";
  vertical-align: super;
  font-size: 0.75em;
}

Programming Reference

DEGREE_SIGN         = "\u00B0"  # °  Generic degree
DEGREE_CELSIUS      = "\u2103"  # ℃  Compatibility — prefer °C
DEGREE_FAHRENHEIT   = "\u2109"  # ℉  Compatibility — prefer °F
MASCULINE_ORDINAL   = "\u00BA"  # º  Spanish/Portuguese ordinal
PRIME               = "\u2032"  # ′  Arc-minutes, feet
DOUBLE_PRIME        = "\u2033"  # ″  Arc-seconds, inches

def format_temperature(value: float, unit: str = "C") -> str:
    """Format a temperature value with the correct degree sign."""
    return f"{value}{DEGREE_SIGN}{unit.upper()}"

print(format_temperature(100))       # 100°C
print(format_temperature(212, "F"))  # 212°F