Nuclear Blast Radius Simulator
Whether you are running a post-apocalyptic tabletop campaign like Fallout: The Roleplaying Game, mapping out a custom survival server, or simply trying to understand the terrifying scale of these weapons, our Nuclear Blast Radius Simulator is the perfect tool for Game Masters and worldbuilders.
By translating complex physics formulas into easy-to-read, game-ready metrics (in kilometers), this simulator allows you to accurately map out destruction zones for your next gaming session.
How to Simulate a Nuclear Blast
Using the simulator requires you to make two major tactical decisions about the weapon your game's villain (or players) are about to deploy.
Step 1: Select Weapon Yield
Choose the payload of your weapon from the dropdown. Yields are measured in Kilotons (KT). Options range from a 1 KT tactical nuke (like the Fallout Fat Man) to the 50,000 KT Tsar Bomba.
Step 2: Choose Burst Type
Select either Airburst or Surface Burst. This drastically changes how the energy is distributed (explained in detail below).
Step 3: Analyze the Zones
Click simulate to view the exact kilometer radius of the four major destruction zones, which you can then draw directly onto your hex map or grid.
Understanding the Blast Zones (Fireball to Fallout)
When a nuclear weapon detonates, it does not just do one type of damage. It unleashes a sequence of catastrophic effects. Our simulator breaks these down into four rings:
- Fireball Radius: The core of the explosion, hotter than the surface of the sun. Everything inside this radius is instantly vaporized. No saving throws.
- Heavy Blast (20 psi): The massive overpressure shockwave. Heavily built concrete buildings are completely demolished. Fatalities approach 100%.
- Thermal Radiation: A blinding flash of light that causes 3rd-degree burns to anyone caught outside. Wood, paper, and clothing spontaneously combust, causing massive firestorms.
- Light Blast (1 psi): The outer edge of the shockwave. Windows shatter, turning glass into deadly shrapnel. Wood-frame houses suffer moderate damage.
Surface Burst vs. Airburst Mechanics
The altitude at which the bomb detonates changes everything about the resulting wasteland.
Airbursts are detonated high above the target. The shockwave travels downward, hits the ground, and reflects outward, merging with the original wave to create a "Mach stem." This drastically increases the radius of the Heavy and Light blast zones. Because the fireball never touches the ground, it does not suck up dirt, meaning local radioactive fallout is minimal.
Surface bursts detonate on or near the ground. Much of the energy is absorbed by the earth, carving a massive crater. The fireball sucks thousands of tons of irradiated dirt into the mushroom cloud, which later rains down. This minimizes the blast radius but creates a lethal, localized fallout zone downwind.
Using Nuke Maps for Tabletop RPGs (Fallout 2d20)
If you are a Game Master running a post-apocalyptic system, this tool is invaluable for worldbuilding.
Grab a real-world map of your city, pick a target (like the downtown financial district or the airport), and run the simulator. Draw the concentric circles on the map. The Fireball zone becomes the "Glowing Sea"—a highly irradiated, melted crater. The Heavy Blast zone becomes a maze of collapsed skyscrapers. The Light Blast zone becomes the scavengable ruins where your players will start their adventure.
Frequently Asked Questions
What is the difference between an airburst and a surface burst?
An airburst detonates high above the target, allowing the shockwave to bounce off the ground and push outward, maximizing the blast radius while creating very little local fallout. A surface burst hits the ground, digging a massive crater and sucking dirt into the mushroom cloud, resulting in lethal local fallout.
How large was the bomb dropped on Hiroshima?
The "Little Boy" bomb dropped on Hiroshima had an estimated yield of 15 Kilotons (KT). Modern strategic weapons are significantly larger, often ranging from 100 KT to 1,000 KT.
Is this tool scientifically accurate?
This simulator uses simplified scaling laws designed for quick reference in tabletop RPGs and educational gaming scenarios. While based on real physics formulas, professional disaster prep should rely on official government tools.
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