What ℼ means
It is a double-struck form of pi for mathematical notation.
A 2004 Unicode proposal labels ℼ lowercase double-struck pi and associates it with 3.14159… William Jones used ordinary π for the circle constant in 1706; Euler later helped popularize it.
When should I use ℼ instead of π?
Use ℼ only when your formula defines it separately.
Fonts may add small finishing strokes without changing ℼ. The 2026 Wolfram Language guide treats double-struck input as a distinct symbol from ordinary π.
Technical math notation; ℼ signals a deliberate symbol choice.
Use π for the circle constant unless a formula calls for ℼ.
Part of the collection
Don't confuse it with
2
Questions people ask
1Why does ℼ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
More like this
11
How to type or find ℼ
- Also called
- blackboard pi · openface pi · bbpi
- Search it as
- ℼ · double struck pi
- Shows up in
- Anything that takes text · its shape is whatever your font draws
ℼ\213CCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.