Asteroid Crater Diameter Calculator

Calculate the transient and final crater diameter from an asteroid impact using the Pi-scaling law.

meters
kg/m³
Rocky asteroid ~3,500 | Iron ~7,874 | Comet ~500
kg/m³
Rock ~2,700 | Sediment ~1,500 | Water ~1,000
km/s
m/s²
degrees
Most probable angle = 45°
Transient Crater
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Final Crater (~1.3×)
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Impact Energy
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How Asteroid Impact Craters Form

When an asteroid strikes a planetary surface at cosmic velocities (typically 15-25 km/s for Earth), the kinetic energy is so immense that both the impactor and target material are vaporized, melted, or shattered. The impact creates a transient cavity that then collapses and modifies into the final crater we observe.

The Pi-Scaling Law

The Pi-scaling law uses dimensional analysis to relate impactor properties to crater size. The transient crater diameter is:

Dtc = 1.16 × (ρi/ρt)1/3 × D0.78 × v0.43 × g-0.22 × sin(θ)1/3

Where D is impactor diameter (m), v is velocity (m/s), g is surface gravity (m/s²), and θ is the impact angle. The final crater is approximately 1.3 times the transient diameter due to rim collapse and ejecta settling.

Impact Angle Effects

The most probable impact angle on a sphere is 45 degrees (not 90 degrees, due to the sine-weighted probability distribution of approach trajectories). At 45 degrees, the effective energy transfer is about 79% of a vertical impact. Very oblique impacts (under 15 degrees) create elongated, butterfly-shaped ejecta patterns and shallower craters.

Famous Impact Craters

The Chicxulub crater (Mexico, 180 km diameter) was formed by a ~12 km asteroid 66 million years ago, triggering the mass extinction that ended the dinosaurs. Meteor Crater (Arizona, 1.2 km) was formed by a ~50 m iron meteorite only 50,000 years ago. The Vredefort crater (South Africa, 300 km) is the largest known impact structure on Earth, formed 2 billion years ago.

Energy Scale

A 1 km asteroid at 20 km/s carries energy equivalent to roughly 50,000 megatons of TNT (about 1 million times the Hiroshima bomb). Even a 50-meter object like the Chelyabinsk meteor (2013) released energy equivalent to 500 kilotons, thirty times the Hiroshima bomb, though most was absorbed by the atmosphere.

Frequently Asked Questions

The Pi-scaling law is a dimensional analysis approach that predicts crater size from impactor properties. It accounts for size, velocity, density contrast, gravity, and angle. It is calibrated against experiments and nuclear test craters.
The transient crater is the initial void at the moment of impact. The final crater is ~1.3x larger due to rim collapse, slumping, and ejecta settling. Very large impacts form complex craters with central peaks and terraced walls.
Impact angle affects energy transfer. Vertical impacts (90°) transfer maximum energy. Oblique impacts spread energy over a larger area, producing smaller craters. The most probable angle is 45° due to geometric probability.
The Chicxulub impactor was approximately 10-15 km in diameter, traveling at ~20 km/s, striking at roughly 60°. It created a 180 km crater and triggered the dinosaur extinction 66 million years ago.
Near-Earth asteroids typically impact at 15-25 km/s. Comets impact at 30-70 km/s due to their elliptical orbits. The minimum impact speed on Earth is ~11.2 km/s (escape velocity).