☢️Radiation Dose & Shielding Calculator - Units, Effective Dose, Half-Value Layer

How to use Radiation Dose & Shielding Calculator

1. 1On the Units & effective dose tab enter a value and unit to see conversions, then choose a radiation type and organ doses to get the effective dose
2. 2On the Dose comparison tab enter a dose in mSv and see where it sits among everyday, medical, regulatory and acute-effect levels
3. 3On the Point-source tab pick a nuclide, activity and distance to get the dose rate, the dose over a stay and the distance needed for a target rate
4. 4On the Shielding & range tab pick a material and thickness to read HVL, TVL, transmission and required thickness, and check whether paper, skin or aluminium stops alpha and beta particles

FAQ

What is the difference between Gy and Sv?

The gray (Gy) is absorbed dose: one joule of energy per kilogram, regardless of radiation type. The sievert (Sv) is equivalent or effective dose. It multiplies the gray by a radiation weighting factor (20 for alpha particles, 1 for gamma and beta, 2.5–20 for neutrons depending on energy) and then weights each organ by its cancer sensitivity. So 1 mGy of whole-body gamma is about 1 mSv, while 1 mGy of alpha to the lung is 20 mSv equivalent dose and 2.4 mSv effective dose. Deterministic effects such as acute radiation syndrome are usually described directly in Gy.

Is a banana really radioactive?

Yes, slightly. Bananas contain potassium, and 0.012% of natural potassium is radioactive K-40. Eating one gives roughly 0.1 µSv, the so-called banana equivalent dose. Your body keeps its potassium level constant and excretes any excess, so the comparison only gives a feel for scale: the world-average natural background of about 2.4 mSv a year equals more than twenty thousand bananas.

Why does doubling the distance cut the dose to a quarter?

A point source emits equally in all directions. The same number of photons crosses every sphere around it, and the sphere's area grows as d², so the dose rate is Ḣ = Γ·A/d². Twice the distance gives a quarter of the rate and ten times the distance gives one percent. This is the distance part of time, distance and shielding. It only holds when you are far from a small source, with no shielding or scatter.

What is a half-value layer, and how much lead stops gamma rays?

The half-value layer (HVL) is the thickness that halves a narrow beam: HVL = ln2/μ, and the tenth-value layer is TVL = ln10/μ. Gamma rays fall off exponentially and are never stopped completely, only reduced to an acceptable level. For the 0.662 MeV gamma rays of Cs-137 the narrow-beam HVL is about 5.5 mm of lead, 3.9 cm of concrete and 8 cm of water. Real broad beams include scattered photons, so practical shields must be thicker and are designed with buildup-factor tables.

Can I use these numbers for real radiation protection?

No. The comparison values are typical published figures, and individual cases vary several-fold. Dose-rate constants differ by 10–20% between sources, and shielding here assumes a narrow beam from a point source, without buildup, geometry or spectrum effects. Use the tool to learn and to build a sense of scale. Real shielding design, medical exposure assessment and emergency decisions need qualified radiation-protection experts and the regulator.