Asteroid Impact Calculator
Use consistent metric units. The angle is measured above the horizontal surface.
Example Data Table
| Scenario | Diameter | Density | Velocity | Angle | Useful purpose |
|---|---|---|---|---|---|
| Small stony body | 5 m | 2,700 kg/m³ | 17 km/s | 45° | Local screening comparison |
| Medium rocky body | 20 m | 3,000 kg/m³ | 20 km/s | 45° | Default learning example |
| Large dense body | 50 m | 3,500 kg/m³ | 25 km/s | 60° | High-energy sensitivity check |
Formula Used
The calculator treats the asteroid as a sphere. It uses standard mass, momentum, and kinetic-energy equations. The crater and blast figures are transparent screening proxies. They are not full physics simulations.
One megaton TNT equals 4.184 × 1015 joules. The target factor is 1.10 for sediment, 0.85 for hard rock, 1.25 for ice, and 0.35 for water.
How to Use This Calculator
- Enter the asteroid diameter in metres.
- Add a realistic bulk density in kilograms per cubic metre.
- Enter approach velocity in kilometres per second.
- Set the impact angle above the horizontal surface.
- Estimate atmospheric energy loss and choose target material.
- Add a reference distance for the energy-flux proxy.
- Select Calculate Impact and review the results above the form.
- Use CSV or PDF download buttons to save the displayed estimate.
Understanding Asteroid Impact Estimates
Why input quality matters
An asteroid impact estimate begins with size, density, speed, and angle. Each value changes the final energy. Diameter has an especially strong effect. Mass grows with the cube of diameter. Doubling diameter produces eight times the volume. A small sizing error can therefore create a large energy difference. Density also matters. Metallic bodies can carry more mass than porous stony bodies of identical size. Velocity affects energy even more strongly. Kinetic energy rises with the square of speed. A body moving twice as fast carries four times the kinetic energy.
What the energy result means
The energy result is shown in joules and TNT equivalents. Joules are the base scientific unit. TNT equivalents help compare large values. A kiloton represents one thousand tonnes of TNT. A megaton represents one million tonnes. These comparisons describe energy, not identical damage. Explosions and impacts release energy differently. Local terrain, airburst altitude, fragmentation, and the target all change outcomes. Treat the displayed yield as a scale indicator. It is not a precise forecast of damage in a named place.
Angle and atmospheric loss
Impact angle affects how directly energy couples to the surface. A near vertical path focuses more motion toward the ground. A shallow path can spread the interaction over a longer distance. This calculator uses the sine of the angle as a clear adjustment. Atmospheric loss reduces the energy available at the surface. Small or weak bodies may break apart. Large dense bodies may retain more energy. Enter a conservative loss when details are unknown. Compare several loss values to understand uncertainty.
Crater and blast screening values
The crater diameter is a screening proxy. It uses effective energy and a target modifier. Soft sediment can form wider structures than hard rock. Water produces different processes and may create waves instead of a conventional crater. The blast radius is also a broad scale estimate. It does not calculate pressure, thermal radiation, winds, or building damage. The energy-flux proxy at the reference distance is simpler still. It helps compare scenarios. Do not use it as an evacuation threshold or engineering design value.
Using results responsibly
Run several scenarios rather than relying on one answer. Test smaller and larger diameters. Change the density and atmospheric loss. Compare shallow and steep angles. Record the assumptions beside each output. This approach reveals which inputs drive the result. This disciplined method makes comparisons clearer, exposes uncertainty early, and prevents a convenient number from being mistaken for a final conclusion. Results should be compared with independent sources before they are shared. State every unit clearly. Keep estimates separate from observations. A calculator cannot determine whether an object will strike Earth, survive the atmosphere, or produce particular local effects without detailed, verified data and expert interpretation. For research, planning, or public safety decisions, use specialist impact models and expert review. They can include entry breakup, ground composition, ocean effects, shock propagation, and geographic exposure. This page is best used for education, rough comparison, and transparent first-pass calculations.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates asteroid mass, kinetic energy, momentum, TNT equivalent, effective ground-coupled energy, and simple crater and blast screening values. It is designed for educational comparisons and early scenario testing.
2. Does it predict a real impact accurately?
No. Real impacts require detailed atmospheric-entry, fragmentation, terrain, and geological modelling. The displayed results are transparent first-pass estimates, not a location-specific prediction.
3. Why is diameter so important?
The calculator models the body as a sphere. Volume, and therefore mass, grows with diameter cubed. Doubling diameter produces eight times the volume when density stays unchanged.
4. Which density should I enter?
Use a justified bulk density. A stony object may be near 2,000 to 3,500 kg/m³. Dense metallic objects may be higher. Porous material may be lower.
5. Is the angle measured from vertical?
No. The angle is measured above the horizontal surface. Enter 90 degrees for a vertical impact and a smaller value for a shallower path.
6. What does atmospheric energy loss represent?
It represents energy removed before surface impact through drag, heating, ablation, and possible breakup. It is a simple user-controlled percentage, not an atmospheric-entry simulation.
7. How is TNT equivalent calculated?
The calculator divides kinetic energy in joules by 4.184 billion joules per tonne of TNT. It then expresses the result in tonnes, kilotons, and megatons.
8. Why is the crater result called a proxy?
Crater size depends on material strength, gravity, impactor shape, fragmentation, and many other effects. This simplified equation gives a comparable screening number rather than a verified crater forecast.
9. Can I use water as the target material?
Yes. Select water to apply a smaller conventional crater modifier. Water impacts can create very different hazards, including waves, so use specialist modelling for coastal risk studies.
10. What is the energy-flux proxy?
It divides effective energy across a hemispherical area at the chosen distance. It helps compare scenarios, but it does not calculate pressure, heat, radiation, or structural damage.
11. Are CSV and PDF downloads available?
Yes. After calculation, use the download buttons beneath the form. The CSV contains the visible result metrics. The PDF contains a formatted summary and selected input values.
Use these estimates responsibly before making important safety decisions.