Asteroid Crater Diameter Calculator
Estimate transient crater size, a simplified final crater diameter, and impact energy from impactor and target conditions.
Last reviewed: June 2026What this crater calculator estimates
This asteroid crater diameter calculator estimates the gravity-regime transient crater diameter from six inputs: impactor diameter, impactor density, target density, impact velocity, surface gravity, and impact angle. It also reports a simplified final crater diameter and the impactor kinetic energy in megatons of TNT equivalent. The goal is to make the scale of an impact scenario easier to compare, not to replace detailed hydrocode simulation or a full planetary defense assessment.
The calculation uses a compact pi-scaling style relationship: crater size grows strongly with impactor size, moderately with velocity, and inversely with surface gravity. Density enters as an impactor-to-target ratio. The angle term uses the sine of the impact angle, so a lower angle from the horizontal reduces the effective vertical component of the impact. A 45° impact angle is often used as a practical default because it is close to the most probable impact angle for randomly oriented impacts.
How to read the outputs
Transient crater is the temporary excavation cavity immediately after impact. It is the bowl or cavity before the rim slumps, ejecta falls back, melt moves, and the structure is modified by gravity and material strength. Final crater on this page is a simple 1.3x multiplier on transient diameter. That is useful for quick comparison, but it is not a morphology model. Real final craters can be simple bowls, complex craters with central peaks, peak-ring basins, or heavily modified scars depending on size, gravity, target layering, and impact energy.
Impact energy is computed from kinetic energy, using mass from the impactor diameter and density. The calculator shows the energy in megatons or kilotons of TNT equivalent and compares it with a 15 kiloton reference. Energy helps compare scenarios, but crater diameter and surface hazard are not one-to-one. An icy body, a weak sediment target, an ocean impact, or an atmospheric airburst can produce very different outcomes from the same kinetic energy.
Worked default example
With the default settings, a 1,000 m rocky asteroid at 3,500 kg/m3 strikes rock at 20 km/s on Earth gravity at 45°. The calculator returns a transient crater of about 10.55 km, a simplified final crater of about 13.71 km, and about 87,600 megatons of impact energy. Those numbers are best read as order-of-magnitude planning values for a crater-scaling exercise. A complete Earth impact effects model would additionally need atmospheric entry, breakup, target geology, ejecta distribution, blast, thermal radiation, seismic shaking, and regional exposure.
Inputs and assumptions
Impactor diameter is the pre-impact body diameter. Doubling this input has a larger effect than doubling velocity because the scaling exponent on diameter is higher and mass also grows with volume for the energy calculation. Impactor density separates porous comet-like bodies from rocky and iron-rich bodies. A denser body of the same diameter carries more mass and typically excavates a larger crater in this simplified model.
Target surface density is the bulk density of the material being excavated, not the average density of the whole planet. Dry sediment, porous regolith, basalt, ice, and water-rich layers behave differently in reality, so choose the value that best represents the near-surface target. Impact velocity should be the speed at contact, after any atmospheric effects if the body is striking Earth. Surface gravity should match the target world. Lower gravity generally allows a larger excavation cavity for the same impactor. Impact angle is measured from the horizontal, so 90° is vertical and a smaller value is more grazing.
Where this simplified model breaks down
This calculator intentionally leaves out strength-regime cratering, atmospheric filtering, impactor fragmentation, target layering, oblique-impact asymmetry, ocean coupling, melt production, ejecta blanket thickness, rim height, and the simple-to-complex transition. It also does not distinguish between a small crater where rock strength dominates and a large basin where gravity and collapse dominate. Use the result as a fast scaling estimate and use more detailed impact-effects tools or mission-grade models for hazard work.
The final-diameter multiplier is deliberately labeled. It gives a quick number that is easy to compare with crater catalogs, but real final diameters can diverge substantially from a fixed factor. On the Moon, Mars, Earth, and icy satellites, crater preservation also differs: erosion, tectonics, volcanism, impact gardening, and burial can change what remains visible long after the initial impact.
Common mistakes to avoid
A common mistake is mixing units. Diameter is entered in meters, velocity in kilometers per second, density in kg/m3, and gravity in m/s2. Another mistake is treating the energy comparison as a damage map. The calculator does not know where people live, whether the body enters through an atmosphere, whether it airbursts, or how ejecta and shock waves propagate.
Do not use Jupiter, Saturn, Uranus, or Neptune as ordinary solid-surface targets for this page. The gravity input can be changed, but the crater model assumes an excavated surface. It is more appropriate for rocky bodies, icy moons, airless bodies, or idealized solid targets where crater-scaling assumptions make sense.
Sources and further reading
This page is a browser implementation of a simplified educational scaling relationship, cross-checked against crater-scaling references and impact-effects teaching tools. Useful starting points include the Earth Impact Effects Program from Purdue University and Imperial College London, its crater-size explanation notes, NASA NTRS material on impact crater scaling laws, and the USGS review of fresh lunar impact crater variations.
Frequently Asked Questions
Quick reference
| Output | What it means |
|---|---|
| Transient crater | Temporary excavation cavity before collapse and fallback modification. |
| Final crater | Simple 1.3x estimate for fast comparison, not a morphology model. |
| Impact energy | Kinetic energy from impactor mass and impact speed, shown as TNT equivalent. |
| Best use | Education, scenario comparison, and first-pass crater-scaling intuition. |