What is the Richter Scale Calculator?

Calculate Richter magnitude, explore earthquake effects, and compare magnitudes with this free Richter scale calculator. Compute ML from Wood-Anderson seismograph amplitude and epicentral distance, look up effects and seismic energy for any ML value, or compare two magnitudes to see amplitude and energy ratios. Each +1 on the Richter scale means 10× ground motion and roughly 31.6× energy. Runs entirely in your browser with no signup.

How to use the Richter Scale Calculator

Choose a mode: From Amplitude, Magnitude Effects, or Compare Magnitudes.
From Amplitude: enter peak trace amplitude in mm and epicentral distance in km to compute ML using the classic Richter formula.
Magnitude Effects: enter any ML value to see category, typical damage, energy, TNT equivalent, and global frequency.
Compare: enter two magnitudes to see the amplitude ratio (10^ΔM) and energy ratio (10^1.5ΔM).
Try presets like ML 5.0, ML 7.0, or compare 9.0 vs 5.0 to see how much stronger a great earthquake is.

Common use cases

Computing ML from a lab seismograph amplitude and station distance
Understanding what ML 4, 5, or 7 means for shaking and damage
Comparing two earthquake magnitudes for a geology homework problem
Explaining why a magnitude 9 earthquake releases vastly more energy than magnitude 5
Quick Richter scale reference alongside the earthquake magnitude converter

Frequently asked questions

What is the Richter scale?: The Richter scale (local magnitude ML) is a logarithmic scale introduced by Charles Richter in 1935. Each whole-number increase means about 10 times greater ground motion amplitude and roughly 31.6 times more seismic energy released.
How is Richter magnitude calculated from amplitude?: This tool uses ML = log₁₀(A) + 2.76 × log₁₀(Δ) + 0.218, where A is the maximum Wood-Anderson seismograph trace amplitude in millimeters and Δ is epicentral distance in kilometers. Regional calibrations may differ.
What does a magnitude 5 earthquake feel like?: ML 5 is classified as moderate — felt by most people indoors and outdoors, with rattling dishes and windows. Minor damage to weak structures is possible, especially near the epicenter.
How much stronger is magnitude 7 than magnitude 5?: The difference is 2 units. Amplitude ratio = 10² = 100× stronger ground motion. Energy ratio = 10^(1.5×2) = 10³ = 1,000× more energy released.
Is Richter magnitude the same as moment magnitude?: Not exactly. ML (Richter) saturates for very large earthquakes, while Mw (moment magnitude) is preferred today for major events. This calculator shows approximate Mw alongside ML for reference.

More Earth Science Tools

What is the Richter Scale Calculator?

How to use the Richter Scale Calculator

Choose a mode: From Amplitude, Magnitude Effects, or Compare Magnitudes.

From Amplitude: enter peak trace amplitude in mm and epicentral distance in km to compute ML using the classic Richter formula.

Magnitude Effects: enter any ML value to see category, typical damage, energy, TNT equivalent, and global frequency.

Compare: enter two magnitudes to see the amplitude ratio (10^ΔM) and energy ratio (10^1.5ΔM).

Try presets like ML 5.0, ML 7.0, or compare 9.0 vs 5.0 to see how much stronger a great earthquake is.

Common use cases

Computing ML from a lab seismograph amplitude and station distance

Understanding what ML 4, 5, or 7 means for shaking and damage

Comparing two earthquake magnitudes for a geology homework problem

Explaining why a magnitude 9 earthquake releases vastly more energy than magnitude 5

Quick Richter scale reference alongside the earthquake magnitude converter

Frequently asked questions

What is the Richter scale?

The Richter scale (local magnitude ML) is a logarithmic scale introduced by Charles Richter in 1935. Each whole-number increase means about 10 times greater ground motion amplitude and roughly 31.6 times more seismic energy released.

How is Richter magnitude calculated from amplitude?

This tool uses ML = log₁₀(A) + 2.76 × log₁₀(Δ) + 0.218, where A is the maximum Wood-Anderson seismograph trace amplitude in millimeters and Δ is epicentral distance in kilometers. Regional calibrations may differ.

What does a magnitude 5 earthquake feel like?

ML 5 is classified as moderate — felt by most people indoors and outdoors, with rattling dishes and windows. Minor damage to weak structures is possible, especially near the epicenter.

How much stronger is magnitude 7 than magnitude 5?

The difference is 2 units. Amplitude ratio = 10² = 100× stronger ground motion. Energy ratio = 10^(1.5×2) = 10³ = 1,000× more energy released.

Is Richter magnitude the same as moment magnitude?

Not exactly. ML (Richter) saturates for very large earthquakes, while Mw (moment magnitude) is preferred today for major events. This calculator shows approximate Mw alongside ML for reference.