Free interactive tool
How much a place cuts your radiation dose from fallout (its protection factor), and how much more you gain by piling earth, water, books or other dense material around you. Add an outside reading to estimate the dose you would get inside.
From the guide Nuclear Event Survival: protection factors →
Every "halving thickness" of material halves the radiation coming through it. Most of the dose comes in a straight line through walls and the roof, so cover the sides and, on a top floor or in a bungalow, overhead too.
The thickness of each material that halves fallout radiation. Two halving thicknesses cut it to a quarter, three to an eighth, and so on.
| Material | Halves it | PF 10 needs about |
|---|
Figures from the Nuclear Event Survival guide's shielding tables (fallout gamma radiation). Protection factors are the guide's typical ranges; this calculator uses the lower figure of each range, so real protection may be better. A filled fridge is roughly PF 6–8, a washing machine filled with sand 10–16. Never block all ventilation: see the guide's section on breathable air.