Earthquake Energy Calculator
Enter an earthquake magnitude and see the energy released in joules and TNT equivalent.
Understand the power behind Richter scale numbers.
How Earthquake Energy Is Calculated
The Richter scale and the moment magnitude scale (Mw) are logarithmic. Each whole number step represents about 31.6 times more energy released.
Energy-Magnitude Formula (Gutenberg-Richter):
log₁₀(E) = 1.5 × M + 4.8
Where:
- E = energy in Joules
- M = moment magnitude (Mw)
Or rearranged: E = 10^(1.5M + 4.8)
Worked Example: Magnitude 7.0 earthquake:
- E = 10^(1.5 × 7.0 + 4.8) = 10^(10.5 + 4.8) = 10^15.3
- E ≈ 2.0 × 10¹⁵ Joules
- Equivalent to about 480 kilotons of TNT
Magnitude 8.0 earthquake (1 point higher):
- E = 10^(12.0 + 4.8) = 10^16.8 ≈ 6.3 × 10¹⁶ Joules
- That is 31.6 times more energy than M7.0
Energy Scale Reference
| Magnitude | Energy | What it does |
|---|---|---|
| M3.0 | 2.0 × 10⁹ J | Felt locally, no damage |
| M5.0 | 2.0 × 10¹² J | Moderate, can crack weak structures |
| M7.0 | 2.0 × 10¹⁵ J | Major, widespread damage |
| M9.0 | 2.0 × 10¹⁸ J | Great, catastrophic across a region |
| M9.5 | 1.1 × 10¹⁹ J | Valdivia, Chile 1960, the largest ever recorded |
Key Insight: The logarithmic scale means M9.0 releases about 1,000 times more energy than M7.0, and about 31,600 times more than M6.0. That exponential scaling is why a small step on the scale means a dramatically more destructive event: a M6.5 causes minor damage where a M7.5 can level a city.
Why the numbers feel too big
The joule figures are genuinely enormous, and they measure the total energy released at the source. Only a small fraction of it, typically a few percent, arrives as the ground shaking that damages buildings; the rest goes into heat and into permanently deforming rock along the fault. That is why a distant M8 can be gentler where you stand than a shallow M5 directly underneath you.
Depth and distance often matter more than magnitude. The 2010 Haiti earthquake was M7.0, the same size as many quakes that pass with little notice, and it killed around 230,000 people because it was shallow, close to a dense city, and the buildings were unreinforced. The 2011 Tohoku earthquake released roughly a thousand times more energy but most of the deaths came from the tsunami rather than the shaking.
Two scales, one number. Reported magnitudes above about M4 are moment magnitude (Mw), which is derived from the fault area, the slip distance and the rigidity of the rock. It was designed to give the same number as Charles Richter’s 1935 local magnitude for moderate events, so the two agree in the middle of the range and diverge at the extremes. The original Richter scale saturates near M7 and cannot distinguish the largest earthquakes at all, which is why nothing modern uses it for big events.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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