Constants & Units · constant

Baryon density

Ω_b h² = 0.022 37 ± 0.000 15 —

Unit

—

Value

0.022 37 ± 0.000 15

Exact

no

Note

Ordinary matter — atoms — comes to under 5% of the total.

Symbol

Ω_b h²

Category

Cosmological

Numeric

0.02237

Uncertainty

±0.000 15 (Planck 2018)

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From the Constants database in Notion, last edited 2026-08-15. This page is the row, rendered by the build; nothing on it is written by hand.