How much energy does an earthquake release?
Magnitude to joules and TNT, a ratio between two quakes, or seismic moment to Mw.
Fill one field. If both are filled, the moment is used.
E in joules. The classic relation (Gutenberg and Richter) gives 31.6 times more energy per step; the USGS page formula gives 27.5.
What the number means
Earthquake magnitude is a logarithmic scale, which is why a small change in the number hides a very large change in energy. The scale measures the source of the shaking, not the shaking at your house: a single event has one magnitude and many different intensities. This calculator converts that magnitude into the seismic energy radiated as waves, puts it next to familiar units (tons of TNT, kilowatt-hours), and shows how much bigger one earthquake is than another.
The formulas
For energy, the classic relation of Gutenberg and Richter is log10 E = 1.5 M + 4.8, with E in joules and M the magnitude. The USGS page on magnitude and energy currently gives log E = 5.24 + 1.44 Mw instead, and calls it a rough estimate, so the calculator lets you pick either. For two earthquakes M1 and M2 the ratio of energies is 10^(a × (M2 − M1)), where a is 1.5 or 1.44, and the ratio of seismogram amplitudes is 10^(M2 − M1). For moment magnitude, Mw = 2/3 × log10 M0 − 10.7 with M0 in dyne-cm, which the calculator converts for you from newton-meters.
Worked example
Magnitude 7 with the classic relation: log E = 1.5 × 7 + 4.8 = 15.3, so E = 10^15.3 = 2.00 × 10^15 J. Dividing by 4.18 × 10^9 J per ton of TNT gives 477 kilotons, and dividing by 3.6 × 10^6 J per kWh gives 554 GWh. A magnitude 6 releases 6.31 × 10^13 J, so the magnitude 7 releases 31.6 times as much, while its seismogram trace is 10 times higher. The step from magnitude 5 to 9 is four whole steps: 1,000,000 times the energy and 10,000 times the amplitude.
Limits of this method
The relations are empirical. Both were fitted to observed earthquakes, and the USGS itself calls the equation rough. The two constants disagree by about 1 times at magnitude 7, and real events scatter around either line, so quote the result as an order of magnitude. The magnitude type matters. The USGS states that older scales can over- or under-estimate very large earthquakes and prefers moment magnitude; a Richter ML of 7 from an old catalog is not the same quantity as a modern Mw 7.0. Energy is not damage. Shaking at a site depends on distance, depth, geology and construction. Energy is not the moment. The seismic moment, which sets Mw, is a measure of fault size and slip, while the radiated energy is a separate quantity; the USGS notes that Mw and the energy magnitude Me measure different properties, so do not read the joules as a precise property of the event.
Common mistakes
Treating magnitude as linear (a 7 is not "a bit more" than a 6); adding magnitudes of aftershocks (energies add, magnitudes do not); and using the moment in dyne-cm in a formula written for newton-meters, which shifts Mw by about 4.7 units. Type moments in N·m here.
Questions
How much more energy does each magnitude step release?
The USGS says each whole-number increase in magnitude releases about 32 times more energy and shows a tenfold larger amplitude on a seismogram. With the classic relation log E = 1.5 M + 4.8 the exact step is 10^1.5 = 31.6. With the formula currently written on the USGS page, log E = 5.24 + 1.44 Mw, it is 10^1.44 = 27.5. Either way a magnitude 8 releases roughly 1,000 times the energy of a magnitude 6 (1,000 times with the classic formula).
What is the energy of a magnitude 7 earthquake?
About 2.00 × 10^15 joules with the classic formula, which is 477 kilotons of TNT, or 554 gigawatt-hours. The USGS-page formula gives 2.09 × 10^15 joules, 499 kilotons. The two differ by a factor of 1 at magnitude 7, which is small next to the uncertainty of the method itself.
Is Richter magnitude the same as moment magnitude?
No. The Richter scale (ML) was devised by Charles Richter in 1935 from the amplitude of waves on a seismograph in Southern California. It saturates for large earthquakes, so the USGS now reports moment magnitude (Mw), based on the seismic moment of the whole rupture, and notes that the Richter scale is now used mainly for small, locally recorded quakes. News reports still say Richter out of habit; the number you see for a large earthquake is Mw.
How is moment magnitude calculated?
Hanks and Kanamori (1979) defined Mw = 2/3 × log10(M0) − 10.7, with the seismic moment M0 in dyne-centimeters. In newton-meters (1 N·m = 10^7 dyne-cm) that is Mw = 2/3 × log10(M0) − 6.03. A moment of 10^22 N·m gives Mw 8.63; going the other way, Mw 7 corresponds to a moment of 3.55 × 10^19 N·m. The moment is rigidity of the rock × area of the fault that slipped × average slip.
Why does bigger energy not always mean more damage?
The USGS points out that the shaking at a site depends on much more than the energy: distance from the rupture, depth, local geology and building construction all matter. A magnitude 7 deep under the ocean may be barely felt on land, while a shallow magnitude 6 under a city can be deadly. Magnitude is a property of the source; intensity (the Modified Mercalli scale) describes what a place experienced.
Is the TNT comparison meaningful?
One ton of TNT is defined as 4.18 × 10^9 joules, so the conversion is exact. But an explosion releases its energy in a fraction of a second at one point, while an earthquake radiates a small share of the energy of the rupture over seconds to minutes across a fault tens or hundreds of kilometers long. The comparison gives a sense of scale, nothing more.
What is the energy magnitude Me?
Choy and Boatwright (1995) defined an energy magnitude Me from the radiated seismic energy measured directly in the broadband P-wave record, using Me = 2/3 log10(Es) − 2.9 with Es in newton-meters. The USGS notes that Me and Mw measure different things, so they need not agree for a given earthquake; Me is tied to damage potential, Mw to the size of the rupture.
Sources: USGS, "Earthquake Magnitude, Energy Release, and Shaking Intensity" (log E = 5.24 + 1.44 Mw; about 32 times the energy and a tenfold amplitude per step; Richter ML now used mainly for small local quakes); Gutenberg and Richter (1956), the relation log E = 1.5 M + 4.8 as widely cited; Hanks and Kanamori (1979), "A moment magnitude scale", Journal of Geophysical Research 84; Choy and Boatwright (1995), energy magnitude as described in USGS NEIC processing notes. A ton of TNT is defined as 4.184 × 10^9 J. Read October 27, 2026. Related: kinetic energy calculator, speed of sound calculator, wind turbine power calculator. How we check our calculators.