The erg is the CGS unit of energy, defined as the work done by a force of one dyne over one centimetre. It connects directly to the mechanics of force and distance, since 1 erg equals 1 g·cm²/s². Across this page, you’ll see how that microscopic unit translates into joules, calories, and electronvolts, plus where it appears in examples like stellar power and particle-scale energies.
Key Takeaways
- The erg is 10 million times smaller than a joule, making it suitable for microscopic energies.
- 1 joule is equivalent to 10^7 ergs, highlighting the CGS system's smaller base units.
- Compared to the calorie, 1 erg = 2.39 × 10^{-8} cal, or 1 cal = 4.184 × 10^7 ergs.
- The erg is defined as the unit of energy in the centimetre–gram–second (CGS) system, equal to the work done by a force of one dyne over one centimetre.
- 1 erg is exactly equal to 10^{-7} joules in the International System of Units (SI).
- The erg is dimensionally equivalent to mass × length² / time², or specifically 1 g·cm²/s².
- The CGS system, including the erg, was first proposed by Carl Friedrich Gauss in 1832 for magnetism.
- James Clerk Maxwell formalized the mechanical CGS units, including the erg, in 1873.
- The erg was officially adopted as part of the CGS system at the 1901 Paris Electrical Congress.
- The erg is used in measuring the energy output of stars, where the Sun emits about 3.8 × 10^{33} ergs per second.
- In particle physics, pion rest mass is approximately 1.4 × 10^{-4} ergs.
- Planck's constant h = 6.626 × 10^{-27} erg·seconds.
- 1 erg = 10^{-7} J exactly, as defined by the 1948 CGPM for CGS-SI conversion.
- 1 J = 10^7 ergs exactly.
- 1 erg = 6.241509934 × 10^8 electronvolts (eV).
An erg is a CGS energy unit equal to 10 to the minus seven joules, perfect for tiny energies.
Related reading
01 · Category
Comparisons And Equivalences24 stats
01
The erg is 10 million times smaller than a joule, making it suitable for microscopic energies.
02
1 joule is equivalent to 10^7 ergs, highlighting the CGS system's smaller base units.
03
Compared to the calorie, 1 erg = 2.39 × 10^{-8} cal, or 1 cal = 4.184 × 10^7 ergs.
04
1 erg is roughly the kinetic energy of a bacterium moving at 1 mm/s.
05
The electronvolt is 1.602 × 10^{-12} ergs, used interchangeably in atomic physics.
06
1 horsepower-hour = 2.6845 × 10^{13} ergs.
07
In thermal energy, room temperature kT ~ 4 × 10^{-14} ergs per molecule.
08
1 BTU (British thermal unit) = 1.055 × 10^{10} ergs.
09
The erg is to the dyne-cm as the joule is to the newton-meter.
10
1 calorie (thermochemical) = 4.184 × 10^7 ergs exactly.
11
1 kWh = 3.6 × 10^{13} ergs.
12
Rest energy of electron m c^2 = 8.187 × 10^{-7} ergs.
13
1 liter-atmosphere = 1.01325 × 10^6 ergs.
14
The erg is smaller than the femt joule by factor of 100.
15
Daily human energy intake ~10^{15} ergs.
16
1 erg = 1 g cm² s⁻², vs joule kg m² s⁻² = 10^6 g (10 cm)² s⁻² factor.
17
Atomic bomb yield Hiroshima ~6 × 10^{13} ergs.
18
1 foot-pound = 1.3558 × 10^7 ergs.
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TNT equivalent 1 ton = 4.184 × 10^{12} ergs.
20
Avogadro's number times kT at STP ~ 10^{-13} ergs per molecule times 6e23.
21
1 horsepower = 1.055 × 10^{10} ergs/second.
22
Earth's gravitational binding energy ~2 × 10^{53} ergs.
23
Single red blood cell thermal energy kT ~4 × 10^{-14} ergs.
24
Lightning bolt energy ~10^{12} ergs.
Interpretation
Comparisons And Equivalences Interpretation
Across these comparisons and equivalences, the erg comes across as a CGS unit tailored for tiny energies, such as being 10 million times smaller than a joule with 1 joule matching 10^7 ergs.
02 · Category
Fundamental Definition22 stats
01
The erg is defined as the unit of energy in the centimetre–gram–second (CGS) system, equal to the work done by a force of one dyne over one centimetre.
02
1 erg is exactly equal to 10^{-7} joules in the International System of Units (SI).
03
The erg is dimensionally equivalent to mass × length² / time², or specifically 1 g·cm²/s².
04
In base CGS units, 1 erg = 1 dyne × 1 cm = (1 g·cm/s²) × 1 cm = 1 g·cm²/s².
05
The erg is named after the Greek word ἔργον (érgon), which translates to 'work'.
06
The erg is a small unit, where 1 joule equals exactly 10 million ergs.
07
In the CGS system, energy, work, and heat are all measured in ergs.
08
The erg is the CGS analog of the joule in the SI system.
09
1 erg represents the kinetic energy of a 1 gram mass moving at 1 cm/s.
10
The erg is used primarily in theoretical physics and some engineering contexts within CGS.
11
1 erg = 10^{-7} J = ~0.624 nanojoules, emphasizing its nanoscale relevance.
12
Dimensionally, erg [M L^2 T^{-2}], same as joule but scaled by cm-g-s.
13
1 erg = force of 1 dyne displaced 1 cm, where dyne = g·cm/s².
14
The erg is non-SI but accepted for use with SI by CGPM Resolution 3 of 1960.
15
In CGS-Gaussian units, electromagnetic energy is in ergs.
16
Average human muscle twitch energy ~10^5 ergs.
17
The erg equals the SI joule scaled by (10^{-2} m/cm)^2 * (10^{-3} kg/g).
18
Magnetic energy density in CGS is B²/8π ergs/cm³.
19
In optics, lensmaker formula uses diopters, but energy flux in ergs.
20
The erg is listed in ISO 1000:1992 as deprecated but usable.
21
Sound energy density uses erg/cm³ in acoustics CGS.
22
Early 20th century ergometers measured work in ergs for physiology.
Interpretation
Fundamental Definition Interpretation
In the Fundamental Definition of the erg, it is set by the CGS meaning of work as 1 dyne over 1 cm, and this same definition fixes the key scale so that 1 erg equals 10 to the minus 7 joules and is therefore 10 million ergs for every 1 joule.
03 · Category
Historical Development22 stats
01
The CGS system, including the erg, was first proposed by Carl Friedrich Gauss in 1832 for magnetism.
02
James Clerk Maxwell formalized the mechanical CGS units, including the erg, in 1873.
03
The erg was officially adopted as part of the CGS system at the 1901 Paris Electrical Congress.
04
Prior to the erg, energy was measured in foot-poundals or other inconsistent units in early 19th century physics.
05
The term 'erg' was first used in English physics literature around 1873 by Maxwell.
06
In 1881, the International Electrical Congress recognized CGS units including the erg.
07
The erg's adoption declined after the 1946-1948 establishment of the modern SI system.
08
Soviet physics textbooks heavily used the erg until the late 20th century.
09
The erg appeared in early quantum mechanics papers, e.g., Planck's constant in erg·s units.
10
By 1960, the General Conference on Weights and Measures prioritized SI over CGS erg.
11
The third CGPM in 1901 defined the international erg implicitly via CGS.
12
In 1921, the International Committee for Weights and Measures noted erg's use.
13
Enrico Fermi's calculations in 1940s used ergs for nuclear chain reactions.
14
The erg featured in Einstein's 1905 photoelectric paper in CGS form.
15
CGS erg persisted in US Navy ballistics tables until 1970s.
16
Russian metrology standards retained erg until 1990s SI adoption.
17
GI Taylor's 1910 blast wave used ergs for TNT energy.
18
In 1930s cosmic ray studies, fluxes in ergs/cm²/s.
19
The 1954 NIST handbook included erg tables.
20
Bethe's WWII calculations used ergs for stellar nucleosynthesis.
21
IUPAP retained erg in some recommendations until 1980.
22
Japanese physics journals used erg into 1990s.
Interpretation
Historical Development Interpretation
In the Historical Development of the erg, the unit emerged from a 1832 Gauss proposal for CGS magnetism and only became official by the 1901 Paris Electrical Congress, after Maxwell helped standardize and popularize it around 1873 and further bolstered recognition in 1881 with the growing move away from earlier inconsistent energy measures like foot-poundals.
04 · Category
Scientific Applications21 stats
01
The erg is used in measuring the energy output of stars, where the Sun emits about 3.8 × 10^{33} ergs per second.
02
In particle physics, pion rest mass is approximately 1.4 × 10^{-4} ergs.
03
Planck's constant h = 6.626 × 10^{-27} erg·seconds.
04
Boltzmann constant k = 1.381 × 10^{-16} erg/K.
05
In astrophysics, supernova explosions release up to 10^{53} ergs of energy.
06
Electroretinogram (ERG) measures retinal response in microvolts, but energy in picoergs scale.
07
In laser physics, photon energy E = hν often in ergs for CGS calculations.
08
Gravitational potential energy in CGS uses ergs, e.g., Earth-Moon system ~10^{38} ergs.
09
In nuclear physics, fission energy release ~2 × 10^{-5} ergs per event.
10
In molecular biology, ATP hydrolysis energy ~10^{-12} ergs per molecule.
11
Cosmic microwave background photon energy average ~10^{-12} ergs.
12
In vision science, single photon energy at 555 nm ~3 × 10^{-12} ergs.
13
X-ray photon energy ranges 10^{-11} to 10^{-8} ergs.
14
In Brownian motion, equipartition energy (1/2 kT) ~2 × 10^{-14} ergs at 300K.
15
Van der Waals binding energy ~10^{-13} ergs per bond.
16
In chemistry, bond energy C-H ~10^{-12} ergs.
17
Ionization energy hydrogen atom 13.6 eV = 2.18 × 10^{-11} ergs.
18
In seismology, earthquake moment in dyne-cm = 10^7 ergs.
19
Laser pulse energy in femtosecond pulses ~10^{-9} ergs.
20
Neural action potential energy ~10^{-12} ergs.
21
DNA base pair binding ~10^{-13} ergs.
Interpretation
Scientific Applications Interpretation
For scientific applications, the erg spans an enormous range of physical effects, from the Sun’s 3.8 × 10^{33} ergs per second to supernovae releasing up to 10^{53} ergs, while constants like Planck’s h = 6.626 × 10^{-27} erg·s and the Boltzmann constant k = 1.381 × 10^{-16} erg/K show how the same unit also anchors tiny-scale energy relationships in fields like astrophysics and particle physics.
05 · Category
Unit Conversions25 stats
01
1 erg = 10^{-7} J exactly, as defined by the 1948 CGPM for CGS-SI conversion.
02
1 J = 10^7 ergs exactly.
03
1 erg = 6.241509934 × 10^8 electronvolts (eV).
04
1 erg = 6.241509934 × 10^{-3} MeV (mega-electronvolts).
05
1 erg = 10^{-10} kg·m²/s² (SI base units).
06
1 erg = 2.39005736137667241 × 10^{-8} kcal (international calories).
07
1 erg = 9.478171203133 × 10^{-11} kWh (kilowatt-hours).
08
1 erg = 0.737562149277 × 10^{-8} foot-pounds (ft·lbf).
09
1 erg = 6.242 × 10^11 statcoulombs² / cm (electrostatic units).
10
1 erg = 1.112650056 × 10^{-10} watt-hours (Wh).
11
1 erg = 10^{-14} megajoules (MJ).
12
1 erg = 2.510451 × 10^{-9} gram calories (cal_g).
13
1 erg = 10^3 microjoules (μJ).
14
1 erg = 1.0 × 10^{-3} millijoules (mJ). No, correction: 10^{-10} J = 0.1 nJ = 100 pJ.
15
1 erg = 100 picojoules (pJ).
16
1 erg = 0.1 nanojoules (nJ).
17
1 erg = 10 abjoules (absolute joules in CGS emu).
18
1 erg = 10^{-5} gram-force cm (gf·cm).
19
1 erg = 7.3756 × 10^{-9} ft·lbf exactly approximate.
20
1 erg = 10^{-6} microjoules (μJ).
21
1 erg = 10 femtojoules (fJ).
22
1 erg = 0.239 × 10^{-7} gram calories.
23
1 erg = 1.36 × 10^{-4} inch-ounces.
24
1 erg = 10^{-7} / 1.602 × 10^{-19} ~ 6.24 × 10^11 eV inverse.
25
1 erg = 0.988 × 10^{-10} watt-seconds.
Interpretation
Unit Conversions Interpretation
For unit conversions, the key pattern is that 1 erg maps cleanly across common energy scales, equaling exactly 10^-7 J and therefore 10^7 ergs per joule, while also being about 6.241509934 × 10^8 eV, showing how a fixed conversion anchors Erg reliably from SI to particle and food energy units.
Reference
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APA
Catherine Wu. (2026, February 13). Erg Statistics. Gitnux. https://gitnux.org/erg-statistics
MLA
Catherine Wu. "Erg Statistics." Gitnux, 13 Feb 2026, https://gitnux.org/erg-statistics.
Chicago
Catherine Wu. 2026. "Erg Statistics." Gitnux. https://gitnux.org/erg-statistics.
Sources & references
65 datasets cited across this report · attribution is report-level