Earthquake magnitude calculator: how much stronger?
This earthquake magnitude calculator compares two earthquakes. According to the Japan Meteorological Agency, one magnitude step means about 32 times the energy and two steps about 1000 times; the USGS adds that each step is a tenfold amplitude on the seismogram. Example: M8 releases about 31.62 times the energy of M7.
Example: Magnitude 1 8 M · Magnitude 2 7 M → Comparison: M 8 releases about 31.62 times the energy of M 7. Source: Japan Meteorological Agency (気象庁), FAQ on seismic intensity and magnitude: as a standard relation, magnitude +1 → about 32 times the energy, +2 → about 1,000 times; one M8 equals about 32 M7 or 1,000 M6 earthquakes (read 10.10.2026). Updated: .
How it is calculated
Magnitude is a logarithmic scale. The USGS explains that each whole-number step means a tenfold amplitude on the seismogram and about 32 times more energy. The Japan Meteorological Agency gives the standard relation: one step about 32 times the energy, two steps about 1000 times – one M8 earthquake corresponds to about 32 M7 or 1000 M6 earthquakes. Because 32 × 32 ≈ 1000, the factor per step is the square root of 1000, i.e. 10^1.5 = 31.62. The calculator therefore uses energy ratio = 10^(1.5 × ΔM).
Energy differences at a glance
| Difference ΔM | Energy | Amplitude |
|---|---|---|
| 0.5 (e.g. M7.0 vs M7.5) | 5.62 times | 3.16 times |
| 1 (M7 vs M8) | 31.62 times | 10 times |
| 2 (M6 vs M8) | 1000 times | 100 times |
| 3 (M5 vs M8) | 31,623 times | 1000 times |
| 4 (M5 vs M9) | 1,000,000 times | 10,000 times |
Even half a step matters: M7.5 releases 5.62 times the energy of M7.0. The result is a ratio; a magnitude difference of 4 equals one million times the energy. How powers of ten work is explained in the logarithm calculator; large ratios like 31,623 are easier to read in the scientific notation converter.
Magnitude is not intensity
An earthquake has one magnitude, but the shaking at a particular place – the intensity – depends mostly on the distance from the fault rupture, and also on the direction of the rupture and the ground beneath you, as the USGS points out. This calculator only compares the energy released at the source.
Frequently asked questions
How much stronger is an M8 earthquake than an M7?
About 31.62 times the energy (JMA: about 32 times) and 10 times the amplitude on the seismogram.
How many M6 earthquakes equal one M8?
About 1000. Two magnitude steps mean 10^3 = 1000 times the energy, as the Japan Meteorological Agency states.
Why is the factor 32 and not 10?
10 applies to the measured amplitude. Energy grows faster: 10^1.5 = 31.62 per magnitude step.
How much more energy is M7.5 than M7.0?
10^(1.5 × 0.5) = 5.62 times as much energy.
Does a higher magnitude always mean stronger shaking where I am?
No. Shaking at a location is the intensity and depends mostly on the distance from the rupture, and also on its direction and the local ground. Magnitude describes the source.
Can I enter decimal magnitudes?
Yes, any value between −2 and 10, e.g. 6.4 and 7.1. The energy ratio for ΔM = 0.7 is 11.22.
Sources and legal basis
- Japan Meteorological Agency (気象庁), FAQ on seismic intensity and magnitude: as a standard relation, magnitude +1 → about 32 times the energy, +2 → about 1,000 times; one M8 equals about 32 M7 or 1,000 M6 earthquakes (read 10.10.2026)
- U.S. Geological Survey, Earthquake Magnitude, Energy Release, and Shaking Intensity: each whole-number step = tenfold amplitude on the seismogram and about 32 times more energy (read 10.10.2026)
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