Earthquake magnitude converter
Enter a known magnitude, energy (J) or TNT equivalent and convert between them using an approximation formula. Specify another magnitude for comparison to view the energy ratio and amplitude ratio separately. Copy all the results together or save them as TXT.
What you can do
Convert earthquake size with an approximate formula
Enter magnitude, energy (J), or TNT equivalent and convert between them as values in the same model.
Compare differences in size as ratios
Specify the magnitude to compare against, and check the energy ratio and amplitude ratio separately.
How to use
Choose the type of value you know
Choose magnitude, energy, or TNT equivalent as the input type, then enter a value.
Enter the magnitude to compare against
Specify the magnitude against which to compare the entered size.
Check converted values and ratios
Select “Convert and compare”. Read the energy and amplitude ratios separately, then copy or save the results if needed.
When to use it
Understand size differences numerically
Learn how the energy ratio changes with differences in magnitude, such as a difference of 1 versus 2.
Check the relationship with energy
Use this to interpret size figures in learning materials and elsewhere as energy or TNT equivalent under the approximate formula.
What magnitude and comparison values mean
Magnitude and seismic intensity are different
Magnitude describes earthquake size; seismic intensity describes the strength of shaking at each location. This conversion cannot determine seismic intensity or damage at particular locations.
Distinguish energy ratios from amplitude ratios
In this model, a magnitude difference of 1 means approximately 31.6 times the energy and 10 times the amplitude. Do not treat the two ratios as meaning the same thing.
TNT is an energy equivalent
Conversion uses 1t TNT = 4.184×10⁹J. This expresses energy in a different unit and does not imply equivalent blast damage.
Frequently asked questions
How many times greater is a magnitude difference of 2?
In this approximation, the energy ratio is 1000 and the amplitude ratio is 100. Reversing the direction of comparison gives the reciprocal of each.
Can I measure the energy of an actual earthquake?
This screen uses an approximate model based on log₁₀E = 1.5M + 4.8. It does not measure individual earthquakes or precisely convert between different magnitude scales.
Can I calculate magnitude from energy?
Yes. Choose energy (J) or TNT equivalent as the input type. Enter a value greater than 0 for either.
Input and results
- Input
- Magnitude, energy, or TNT equivalent, plus the magnitude to compare against.
- Results
- 3 measures of size and 2 comparison ratios from the same approximate model.
- Save
- Copy all 5 values together or save them as TXT. Changing the input clears the previous results.