What is the Earthquake Magnitude Converter?

Convert between earthquake magnitude scales with this free earthquake magnitude converter. Enter a value on Mw (moment magnitude), Ms (surface wave), ML (Richter/local), mb (body wave), or Md (duration) and instantly see equivalent magnitudes on all other scales, plus seismic moment, radiated energy in joules, and TNT equivalent. Uses standard seismological relationships with clear steps. Runs entirely in your browser with no signup.

How to use the Earthquake Magnitude Converter

Enter the earthquake magnitude value (e.g. 5.0, 6.7, or 9.0).
Select the input scale: Mw, Ms, ML, mb, or Md.
Results update instantly — all five magnitude scales, seismic moment M₀, energy E, and TNT equivalent.
Try presets such as Mw 7.0 (major), Mw 9.0 (Tohoku), or ML 6.7 (Northridge).
Copy the full summary with conversion steps for homework or reports.

Common use cases

Converting a reported ML value to Mw for a geology or earth science assignment
Estimating TNT equivalent and seismic energy for a magnitude 7 or 9 earthquake
Comparing Richter, surface wave, and moment magnitude for the same event
Understanding why the 2011 Tohoku earthquake (Mw 9.0) released vastly more energy than a Mw 5.0 tremor
Quick reference when reading USGS or EMSC earthquake bulletins

Frequently asked questions

What is the difference between Richter and moment magnitude?: ML (local/Richter) was the original logarithmic scale based on seismograph readings. Mw (moment magnitude) is derived from the earthquake's seismic moment (fault area × slip × rigidity) and does not saturate for very large events. News reports today usually cite Mw for major earthquakes.
How accurate are magnitude scale conversions?: Conversions between Ms, ML, mb, and Mw are empirical approximations that vary by region, depth, and frequency band. This tool uses global average relationships suitable for education and quick estimates — not for official catalog work.
How is seismic energy calculated?: Radiated energy is estimated from moment magnitude using the Kanamori relation: log₁₀(E) = 1.5 × Mw + 4.8, where E is in joules. TNT equivalent divides E by 4.184 × 10⁹ joules per ton of TNT.
What is seismic moment?: Seismic moment M₀ (in newton-meters) measures the total energy released by fault slip. It relates to Mw by log₁₀(M₀) = 1.5 × Mw + 9.1. Larger M₀ means a bigger fault area, more slip, or both.
Why do different agencies report different magnitudes?: Agencies may use different scales (Ms vs Mw), magnitude formulas, station networks, and averaging windows. Early 'quick' magnitudes are often revised as more data arrive.

More Earth Science Tools

What is the Earthquake Magnitude Converter?

How to use the Earthquake Magnitude Converter

Enter the earthquake magnitude value (e.g. 5.0, 6.7, or 9.0).

Select the input scale: Mw, Ms, ML, mb, or Md.

Results update instantly — all five magnitude scales, seismic moment M₀, energy E, and TNT equivalent.

Try presets such as Mw 7.0 (major), Mw 9.0 (Tohoku), or ML 6.7 (Northridge).

Copy the full summary with conversion steps for homework or reports.

Common use cases

Converting a reported ML value to Mw for a geology or earth science assignment

Estimating TNT equivalent and seismic energy for a magnitude 7 or 9 earthquake

Comparing Richter, surface wave, and moment magnitude for the same event

Understanding why the 2011 Tohoku earthquake (Mw 9.0) released vastly more energy than a Mw 5.0 tremor

Quick reference when reading USGS or EMSC earthquake bulletins

Frequently asked questions

What is the difference between Richter and moment magnitude?

ML (local/Richter) was the original logarithmic scale based on seismograph readings. Mw (moment magnitude) is derived from the earthquake's seismic moment (fault area × slip × rigidity) and does not saturate for very large events. News reports today usually cite Mw for major earthquakes.

How accurate are magnitude scale conversions?

Conversions between Ms, ML, mb, and Mw are empirical approximations that vary by region, depth, and frequency band. This tool uses global average relationships suitable for education and quick estimates — not for official catalog work.

How is seismic energy calculated?

Radiated energy is estimated from moment magnitude using the Kanamori relation: log₁₀(E) = 1.5 × Mw + 4.8, where E is in joules. TNT equivalent divides E by 4.184 × 10⁹ joules per ton of TNT.

What is seismic moment?

Seismic moment M₀ (in newton-meters) measures the total energy released by fault slip. It relates to Mw by log₁₀(M₀) = 1.5 × Mw + 9.1. Larger M₀ means a bigger fault area, more slip, or both.

Why do different agencies report different magnitudes?

Agencies may use different scales (Ms vs Mw), magnitude formulas, station networks, and averaging windows. Early 'quick' magnitudes are often revised as more data arrive.