GOAT LabPhysRef: Physical Constants & Unit Converter
PhysRef is a free static reference for 4,016 physical constants and a 24,182-pair unit converter (1,192 units across 47 quantities). Every value names the reference it was taken from — 188 distinct sources in all, of which CODATA 2018 supplies 172. Search by name, symbol, or alias and copy any value as plain text, value+unit, LaTeX, or Python.
- Free
- No sign-up
- Works offline
What is PhysRef?
PhysRef is a browser-based physics reference combining a searchable table of 4,016 physical constants in 15 categories with a unit converter spanning 1,192 units and 47 quantities. Values are stored as strings to preserve full precision, and each one carries its own cited source rather than being attributed to a single authority.
How does it work?
Type a name, symbol, or alias (e.g. "planck", "c", "eV") into the cross-search to filter constants and conversion factors instantly. Open a constant for its value, unit, uncertainty, formula, and source. Pick a quantity in the converter, enter a value, and either field recomputes via value_si = value_unit × si_factor + si_offset.
When should I use it?
Use PhysRef when you need an exact constant value, its uncertainty, or a unit conversion factor for homework, lab work, papers, or code. The copy-as-LaTeX and copy-as-Python formats suit writing manuscripts or scripting calculations. It runs offline as a PWA and works without an account.
At a glance
| Physical constants | 4,016 across 15 categories, 188 cited sources |
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| Physical unit converter | 1,192 units, 47 quantities, 24,182 conversion pairs |
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| Uncertainty coverage | 97 exact, 241 with a stated uncertainty, 3,678 not stated in source |
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| Sources | 188 cited; largest CRC Handbook of Chemistry and Physics, 100th ed. (870); CODATA 2018 supplies 172 (4.3%) |
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| Speed of light | c = 299,792,458 m/s (exact) |
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| Planck constant | h = 6.62607015×10⁻³⁴ J/Hz (exact) |
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| Avogadro constant | N_A = 6.02214076×10²³ mol⁻¹ (exact) |
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| Boltzmann / gas constant | k_B = 1.380649×10⁻²³ J/K; R = 8.314462618 J·mol⁻¹·K⁻¹ |
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| Copy formats | Plain, value+unit, LaTeX, Python (4/6/full digits) |
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| Data version | v0.13.0, updated 2026-08-27, CC BY 4.0 |
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Frequently asked questions
What is the value of the speed of light in PhysRef?
PhysRef gives the speed of light in vacuum as c = 299,792,458 m/s, an exact defining constant of the SI (zero uncertainty), sourced from CODATA 2018. A CGS alternative of 2.99792458×10^10 cm/s is also listed.
How many constants and conversions does PhysRef have?
PhysRef contains 4,016 physical constants across 15 categories, plus 1,192 units across 47 quantities and 24,182 unit-pair conversions. Of the constants, 97 are exact (defined, derived, or mathematical) and 241 carry a stated standard uncertainty. The remaining 3,678 (92% of the table) are quoted from a source that gives no uncertainty, and the app says so on the record instead of leaving the field blank.
Which sources are the values from?
Every entry names and links its own source; the table cites 188 distinct sources in all. The most-cited are CRC Handbook of Chemistry and Physics, 100th ed. (870), CRC Handbook of Chemistry and Physics, 100th ed. / MatWeb (653), AME2020 atomic mass evaluation (339). CODATA 2018 accounts for 172 entries (4.3%), chiefly the SI defining constants, so PhysRef is not a CODATA-only table. Other values come from Particle Data Group 2024, NIST, IUPAC (CIAAW 2021), NASA/JPL fact sheets, and the BIPM SI Brochure. License: CC BY 4.0.
Can I copy values as LaTeX or Python?
Yes. Each value can be copied in four formats: plain value, value + unit, LaTeX, or Python. The copied number follows the precision you choose (4 digits, 6 digits, or full precision).
Does PhysRef need an account or internet?
No. PhysRef is free, requires no signup, and works offline as a PWA after first load. The UI is available in English, Japanese, Spanish, Chinese, and German.
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