Blast Radius Calculator

Hopkinson-Cranz Blast Scaling

Explosive effects scale with the cube root of yield. Two blasts produce similar shock profiles when the scaled distance $Z = R / W^{1/3}$ matches, where $R$ is standoff distance and $W$ is TNT equivalent mass in kilograms.

Standoff Distance Formula

$$ R = Z \cdot W^{1/3} $$

This calculator estimates standoff distances for 1, 5, and 20 psi overpressure zones using standard scaled-distance values for TNT in free air. Results are planning estimates only — real safety margins must follow official guidance.

Frequently Asked Questions

What is Hopkinson-Cranz scaling?

It states that blast waves from geometrically similar explosives are comparable when scaled distance Z = R/W^(1/3) is equal.

What does 5 psi overpressure mean?

About 34 kPa peak overpressure. At this level, typical residential structures suffer moderate to severe damage.

Can I enter yield in metric tons?

Yes. Select metric tons; the calculator converts to kilograms before applying the cube-root scaling law.

Is it safe to stand at the calculated distance?

No calculator replaces professional range-safety analysis. Treat all outputs as educational estimates only.

How far is 1 psi for 1 kg TNT?

Using Z ≈ 84.3 m/kg^(1/3), the 1 psi standoff is about 84 m for 1 kg TNT equivalent.

Why use W^(1/3)?

Blast energy scales with mass while shock intensity at a given overpressure scales with distance cubed, giving the cube-root relationship.

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Hopkinson-Cranz Blast Scaling

Standoff Distance Formula

Frequently Asked Questions

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