GOAT LabPhysRef: Physical Constants & Unit Converter
PhysRef is a free static reference for 4,016 CODATA-sourced physical constants and a 24,460-pair unit converter (1,192 units across 44 quantities). 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 44 quantities. Values are sourced from CODATA 2018, CRC Handbook, PDG 2024, NIST, IUPAC, and BIPM, and stored as strings to preserve full precision.
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 (CODATA 2018-sourced) |
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| Physical unit converter | 1,192 units, 44 quantities, 24,460 conversion pairs |
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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 | v0.12.0, updated 2026-04-29, 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 44 quantities and 24,460 unit-pair conversions. Of the constants, 373 are exact defining values; the rest carry stated uncertainties.
Which sources are the values from?
Values come from CODATA 2018, the CRC Handbook of Chemistry and Physics (100th ed.), the AME2020 atomic mass evaluation, Particle Data Group 2024, NIST, IUPAC (CIAAW 2021), and the BIPM SI Brochure. Each entry links its source URL. 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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