Earthquake Magnitude Calculator
Compare earthquake magnitudes: shaking, energy and TNT equivalent.
About this tool
Enter two magnitudes to see how much bigger one is than the other in ground-shaking amplitude and in energy, with each quake's energy in joules, its TNT equivalent and typical effects.
Why each step on the scale matters so much
Earthquake magnitudes are logarithmic. One whole step means about 10 times the amplitude of ground motion on a seismogram and about 32 times the energy (10 to the power 1.5). Two steps means 100 times the amplitude and 1,000 times the energy. So a magnitude 7 releases about 32 times the energy of a 6, and a magnitude 9 about 32,000 times. Energy uses the GutenbergβRichter relation logββ E = 1.5M + 4.8 (joules); a magnitude 6 releases about 6 Γ 10ΒΉΒ³ J, roughly 15 kilotons of TNT, similar to the Hiroshima bomb. Typical effects range from not felt below about 2.5 to widespread destruction above 8. Honest limits: modern reports give moment magnitude (Mw), which these formulas approximate; the damage a quake causes depends far more on depth, distance, ground conditions and building quality than on magnitude, and is described by intensity scales such as Modified Mercalli. The scientific notation converter and the log calculator are related.
Frequently asked questions
How much stronger is a magnitude 7 than a 6?
About 10 times the shaking amplitude and about 32 times the energy released.
How much energy is a magnitude 6 earthquake?
About 6 Γ 10^13 joules, roughly 15 kilotons of TNT.
Is the Richter scale still used?
Seismologists now mostly report moment magnitude (Mw), which is calibrated to give similar numbers for moderate quakes.
Does a bigger magnitude always mean more damage?
No. Depth, distance from towns, soil and building standards often matter more.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.