Calculator

Gamma dose rate calculator

Air-kerma rate falls with the square of distance: doubling the distance quarters the rate. Calculate Γδ from the listed photon energies and yields above 20 keV, then apply activity, distance and optional shielding.

Gamma dose rate calculator

Calculate air kerma from an isotropic point gamma source: K̇ = Γδ A / d², with optional shielding.

m
mm

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Γδ = Σ Eᵢ Yᵢ (μen/ρ)air(Eᵢ) / (4π); K̇ = Γδ A / d² × exp(−μx).

Air kerma (collision), mu_en/rho; H*(10) is not calculated. Each photon line is attenuated at its own energy; broad-beam scatter is excluded (no build-up factor).

Computed from the listed lines only; weak lines and unresolved X-ray groups may be missing. Cs-137 assumes Ba-137m equilibrium at 94.7% branching. Ge-68 assumes equilibrium Ga-68.

Computed constants (photons above 20 keV)

IsotopeΓδ (Gy m² GBq⁻¹ h⁻¹)At 1 m per MBq (µGy/h)
F-180.00013450.1345
Na-220.00028020.2802
K-400.000018330.01833
Co-570.000013340.01334
Co-600.00030560.3056
Ga-680.00012860.1286
Ge-680.00012860.1286
Zr-890.00015050.1505
Mo-990.000018490.01849
Tc-99m0.000014170.01417
In-1110.000047730.04773
I-1230.000017010.01701
I-1250.0000010410.001041
I-1310.000050230.05023
Xe-1330.0000033540.003354
Cs-1370.000076780.07678
Ba-1330.000047050.04705
Ba-137m0.000081080.08108
Sm-1530.0000037420.003742
Lu-1770.0000036180.003618
Yb-1690.000020830.02083
Ir-1920.00010880.1088
Tl-2010.0000024960.002496
Ra-2230.0000090130.009013
Ra-2268.016e-70.0008016
Rn-2225.253e-80.00005253
Th-2322.563e-80.00002563
U-2350.000017020.01702
U-2387.353e-90.000007353
Pu-2393.902e-90.000003902
Am-2410.0000036840.003684
Cf-2523.062e-90.000003062
Se-750.000046650.04665
Kr-853.035e-70.0003035
Pb-2104.385e-70.0004385

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ScienceShot. Gamma dose rate calculator. https://scienceshot.com/gamma-dose-rate-calculator.

Computed from NNDC NuDat 3 line data and NIST SRD 126 air mu_en/rho: NNDC NuDat 3; NIST SRD 126. Resolved Ba-137m and Ir-192 photon supplements: LNHB; shielding: NIST XCOM and ESTAR; SI: BIPM / CODATA 2018. LNHB Ba-137m; LNHB Ir-192; NIST XCOM; NIST ESTAR; BIPM SI.

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Cite this page

ScienceShot. (2026). Gamma dose rate calculator [Online calculator]. https://scienceshot.com/gamma-dose-rate-calculator

@misc{scienceshot-gamma-dose-rate-calculator-2026,
  author = {{ScienceShot}},
  title  = {{Gamma dose rate calculator}},
  year   = {2026},
  note   = {Online calculator},
  url    = {https://scienceshot.com/gamma-dose-rate-calculator}
}