HVL / TVL Shielding Attenuation

Calculate the transmission through shielding from its half-value layer, or the thickness needed for a given reduction, free online.

HVL of the material (mm)

Shield thickness (mm)

Required reduction factor (e.g. 100 = 1% passes) — optional (optional)

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Each half-value layer (HVL) halves the radiation: transmission = 0.5^(thickness ÷ HVL). A tenth-value layer is TVL = 3.32 × HVL. For a required reduction factor F the thickness is HVL × log₂ F. HVL values depend on material and photon energy (e.g. lead ≈ 0.4 mm at 100 kVp X-rays, ≈ 6.5 mm for Cs-137).