Science Symbols

Tap a symbol to copy it. Each shows its Unicode name and code point, with notes on the sign characters that are not the plain letters they look like.

By Maya Chen, lettering designer and type educator · Checked by Jordan Hale · October 2026 · How we review content

Units and temperature

Unit signs that have a single-character form, and the plain-text way to write each.

Physics letters and constants

Letters standing for constants and quantities in physics; check the quantity before you reuse one.

Chemistry reaction arrows

Single-character arrows for reactions and equilibria.

Subscripts, charges and ratios

For formulas like H₂O and SO₄²⁻ when a formatted subscript is not available.

Percent, per mille and counts

Proportions smaller than a percent, plus signs for approximate and proportional values.

Lab and hazard signs

Pictograph characters, shown as colour emoji on many phones.

Astronomy and biology signs

Sun, moon and planet signs, and the female and male signs used in biology.

86 symbols on this page. Names are the official Unicode character names; "emoji" marks characters that often appear as colour pictures on phones.

Sign characters and plain letters

A lot of science notation looks like ordinary letters. Unicode keeps a handful of dedicated characters for historical reasons, which makes copying and pasting riskier than it needs to be.

You see	It may be	Code point	The one to prefer
Å	ANGSTROM SIGN	U+212B	Å, U+00C5
Ω	OHM SIGN	U+2126	Ω, U+03A9 (Greek capital omega)
K	KELVIN SIGN	U+212A	K, U+004B
µ	MICRO SIGN	U+00B5	μ, U+03BC (Greek small mu)
℃	DEGREE CELSIUS	U+2103	° (U+00B0) then C
ℓ	SCRIPT SMALL L	U+2113	l, or write “litre” in full

For the first three, Unicode defines the sign as canonically equivalent to the plain letter, so any normalising software will fold them for you. For the micro sign, folding happens only under compatibility normalisation (NFKC). If you paste into a document that will be searched, prefer the letter over the sign. The Greek alphabet Unicode page goes further into the micro and ohm cases.

The first unit-and-temperature group also lists the square CJK unit characters ㎏㎖㎡㎝㎜㎞㎐. They exist for East Asian typesetting and work fine on screen, but they are not the SI unit symbols. SI writes kg, mL, m², cm, mm, km and Hz with ordinary letters, so use those.

Constants and physics letters

The letters ℎ (PLANCK CONSTANT, U+210E) and ℏ (PLANCK CONSTANT OVER TWO PI, U+210F) are Letterlike Symbols meant for exactly those two constants. They fold to a plain h and to ħ (LATIN SMALL LETTER H WITH STROKE, U+0127) under NFKC, and many people type ħ instead of ℏ. The letter ħ looks right in most fonts; ℏ is more exact when you want the constant’s own code point.

The Greek letters in the second group are the common quantity symbols: λ for wavelength, ν for frequency in many texts, ω for angular frequency, ρ for density, σ and τ for stress, and so on. These are conventions, and the same letter means different things in different fields. The Greek letters in math and science page lists them letter by letter with the standards behind them.

Chemistry arrows, subscripts and charges

For a one-way reaction, → (RIGHTWARDS ARROW) is enough, and ⟶ is a longer version for longer labels. Equilibrium arrows are ⇌ and ⇄, and ⇋ and ⇆ are the mirror images. Up and down arrows ↑ and ↓ mark a gas given off and a precipitate formed in some textbooks.

In running text you can write formulas such as H₂O, CO₂ and SO₄²⁻ using the subscript and superscript digits. They are plain Unicode text, so they paste anywhere, but they are not a replacement for real subscript formatting in a lab report. In a document editor, formatted subscripts also keep the characters searchable as ordinary digits.

Percent, per mille and tolerances

‰ (PER MILLE SIGN, U+2030) means parts per thousand, and ‱ (PER TEN THOUSAND SIGN, U+2031) parts per ten thousand. Isotope ratios and salinity are often quoted in per mille. ± shows a tolerance, ≈ means approximately, and ∝ means proportional to. For the fuller list of operators see math symbols.

Lab, hazard and astronomy signs

The hazard group is a set of pictographs, not the official safety pictograms. Real hazard labelling follows regulations (for example the GHS pictograms), which use their own artwork, so do not use these characters on a label. They suit notes, slides and chat.

The astronomy and biology signs are historical symbols: ☉ for the sun, ♁ for Earth, ♀ and ♂ for female and male in biology. Some phones draw ♀ and ♂ in colour. The Moon sign here is the FIRST QUARTER MOON character, which is commonly used as the crescent moon symbol; its Unicode name describes a phase, so describe it that way if you label it for a screen reader.

Typing them

Each symbol on this page can be copied with one tap. To type them from a keyboard, how to type Greek letters covers the Unicode input methods for Windows, Mac and phones; they work for any character by code point. For the degree sign alone, see the degree symbol page.

Sources

Names, code points and normalisation results were checked with Python 3 unicodedata. The space before °C and the SI unit spellings follow the SI Brochure; the angstrom definition is standard.

Frequently asked questions

What is the difference between µ and μ?

µ is MICRO SIGN (U+00B5), kept from the Latin-1 character set, and μ is GREEK SMALL LETTER MU (U+03BC). They look the same, and both are used for the micro prefix. NFKC normalisation turns the micro sign into the Greek letter, so the Greek letter is the safer choice when text will be searched or compared. For a unit such as µm, either way works on screen, but be consistent inside one document.

Is the Å in angstrom a special character?

Unicode has a separate ANGSTROM SIGN Å (U+212B), but it normalises to the ordinary Å, LATIN CAPITAL LETTER A WITH RING ABOVE (U+00C5), under both NFC and NFKC. Use U+00C5, which is what keyboards and fonts produce. The angstrom is a non-SI unit equal to 10 to the minus 10 metres, still common in crystallography and spectroscopy. The same pattern holds for the ohm sign Ω (U+2126) and the Kelvin sign K (U+212A): the plain letter is preferred.

Should I use ℃ or °C?

Use °C, a degree sign followed by a capital C. ℃ is a compatibility character that Unicode keeps for East Asian text, and it normalises to °C under NFKC. The SI style puts a space between the number and °C, as in 25 °C. The separate degree page has typing shortcuts and the lookalikes to avoid.

Which arrow shows a reversible reaction?

⇌ (RIGHTWARDS HARPOON OVER LEFTWARDS HARPOON, U+21CC) is the common choice for equilibrium, and ⇄ (U+21C4) is also used. Both are widely supported. ⇋ is the mirror image. Many style guides use the harpoon form for equilibria, but textbooks vary, so follow the one your course or journal uses.

How do I write H₂O or Fe³⁺ in plain text?

Use the subscript and superscript digits in the groups above: H₂O is H followed by SUBSCRIPT TWO (U+2082) and O, and Fe³⁺ uses SUPERSCRIPT THREE (U+00B3) and SUPERSCRIPT PLUS SIGN (U+207A). They work in chat, spreadsheet cells and file names, but only the digits 0 to 9 and a few signs exist, so a formula that needs other subscripts will need a proper formatting tool. Most fonts draw them smaller than normal digits, and they can be hard to read at small sizes.

Why do the hazard signs look like emoji?

Characters such as ☢ RADIOACTIVE SIGN and ⚠ WARNING SIGN are in the Miscellaneous Symbols block, and many phones draw them as colour emoji. The code point is the same, but the look depends on the app and font, so check a copy in your target app before you rely on it. Adding the text-style selector (U+FE0E) after the character asks for the plain black-and-white glyph, but not every app respects it.