How much shielding do I need?

Enter the source, its activity and your distance. The page follows the activity into a dose rate, then into the thickness of shield that brings it down to your target.

1 GBq of Cs-137 at 1 m gives 76.8 µGy/h. Behind 10 mm of lead it falls to 21.7 µGy/h. To reach 10 µGy/h you need 17 mm of lead.

  1. Step 1. How much activity is left?

    The activity after the time you set, with any daughter nuclides.

    Enable JavaScript to calculate.

  2. Step 2. What dose rate does it give?

    Air kerma rate at your distance, in the open and behind the shield.

    m
    mm

    Enable JavaScript to calculate air kerma.

  3. Step 3. How much does the shield cut?

    Transmission and half-value layer at the line that carries most of the dose.

    keV
    mm

    The calculator needs JavaScript. The reference values below are computed by the same code.

Result

Shield needed 17 mm

10 mm of lead is not enough. Add 7 mm to reach 10 µGy/h.

Cite this

ScienceShot. How much shielding do I need? https://scienceshot.com/radiation-shielding-calculator.

More formats

ScienceShot. (2026). How much shielding do I need? [Online calculator]. https://scienceshot.com/radiation-shielding-calculator

@misc{scienceshot-radiation-shielding-calculator-2026,
  author = {{ScienceShot},
  title  = {{How much shielding do I need?}},
  year   = {2026},
  note   = {Online calculator},
  url    = {https://scienceshot.com/radiation-shielding-calculator}
}

Sources: NNDC NuDat 3; NIST SRD 126; NIST XCOM; CODATA 2018.

Reviewed by a physicist with CERN experience