Diagnostic X-ray Shielding / Transmission Calculator
Published: Aug 23, 2025
Source: Ionactive Radiation Protection Resource
Diagnostic X-ray Shielding / Transmission Calculator
Diagnostic X-ray
Shielding / Transmission Calculator
Formal advice
If you are after formal advice on x-ray shielding then head over to our Radiation Protection Adviser (RPA) services , or try our online radiation protection training courses for in-depth study on radiation shielding concepts.
Release notes
Version 1.1. Diagnostic X-ray Shielding / Transmission Calculator.
[Version 1.1 - May 2026. A small tweak to add attenuation data to the results as well as transmission - a suggestion by our users].
The data in this calculator is derived mostly from Simpkin 1989; this used Monte Carlo simulation to calculate broad constant potential x-ray beam transmission based on a set of real measurements. The data was then fitted to a model by Archer et al (1983), which was further enhanced by Simpkin 1995. The data noted is widely available online and in publications such as the Handbook of Health Physics & Radiological Health (3rd / 4th edition). It is likely that many interested practitioners may have turned this data into their own private excel spreadsheet calculators. As far as we can tell our calculator is the first time we have seen online resource present the data in an easily accessible form.
Some care and interpretation is required when using this calculator. Many users may be surprised at how the initial apparent (base) TVT or TVL is less than they have seen reported in other literature. In some cases this fact can be used to avoid over designing a shield (for something like an small x-ray shielding cabinet enclosing a research x-ray system running up to 70 kVp with minimal attenuation). However, when this data is used for medical diagnostic x-ray shielding, the user needs to carefully consider x-ray beam hardening (e.g. through the patient). Beam hardening increases the average photon energy, and for heavily attenuated beams it is often the case that a standard (or limiting) HVT is used. The user can see this effect in the calculator by comparing the base HVT (in mm) for a transmission of 0.5, with a transmission of say 0.54 (i.e 0.0825) - some examples of this will be given in the calculator user note below.
X-ray tube output? It is best to either measure x-ray tube output (dose rate) with a sensitive monitor and / or use product literature (which does not always include what you need). If you need a figure to work with then consider our X-ray Tube Dose Rate Calculator Widget (but read carefully the limitations of use). Alternatively, you may also find the following Ionactive article useful: Calculate an estimate of x-ray dose rate from an x-ray tube given kV and mA.
Calculator use notes
Most functions and settings are self-explanatory but we will highlight some key points below. If you make a change to many of the parameters or inputs, please ensure you use the calculate button to use the most recent settings or display updated selections and results.
The calculator can be used to provide a basic set of results for calculating thickness or transmission, or additional tools can be selected (such as inferring transmission from two different dose rates, or applying transmission to a dose rate from a given thickness).
- Material - choose from six potential shielding materials.
- Tube potential (kVp) - select a potential between 25-150 kVP. A drop down menu allows kVp to be selected in 5 kVp lots, or an exact figure can be typed in.
- Modes - two modes are available: Thickness to transmission (default) or dose rate ratio / transmission to thickness. Some of the remaining selectors and input fields described below will depend on the mode setting.
- Thickness - This appears by default (i.e. within the thickness to transmission mode). Enter the thickness (choose your preferred units).
If the dose rate ratio / transmission to thickness mode is selected then further options appear.
- Dose rate ratio before / after - This setting appears by default. To use this feature select use dose rates to infer T from the additional tools menu on the right hand side. Provide before and after shielding dose rates (i.e. the after shielding dose rate is desired, the before shielding dose rate is known or estimated). Clicking calculate will output the transmission with additional supporting data. Alternatively, select transmission from the left hand input method and enter a transmission factor directly (this does not use the additional tools menu).
- Apply to dose rate - this option in the additional tools menu can be selected if the mode is set to thickness to transmission. With this option you can select a thickness, and apply it to a dose rate and see the resulting shielded dose rate upon clicking calculate.
Results and analysis
A neat way to describe this section is by way of an example. The calculator is set up with the following settings:
- Material - lead.
- Tube potential - 100 kVp.
- Mode - Dose rate / transmission → thickness.
- Input method - transmission T (0-1).
- Direct transmission - set to 0.1 (i.e. the user sets T=0.1).
The results and analysis are then calculated and displayed as follows (with our own comments in red where appropriate).
- Required thickness
0.2684 mm - Transmission used
1.000000e-1 (10 %) - Analysis @ 100 kVp
Current thickness: 0.2684 mm [as calculated]
Baseline: HVT₀ = 0.0489 mm · TVT₀ = 0.2684 mm [the baseline initial values]
Next ½: Δ0.1518 mm → 0.4202 mm [next 1/2 value - mm change required & new thickness]
Next 1/10: Δ0.6265 mm → 0.895 mm [next 1/10 value - mm change required & new thickness]
Effective shielding: HVTs ≈ 3.322, TVTs ≈ 1.000
Material: Lead · kVp used: 100
Take a close look at the above data. Note that the baseline implied TVT is 0.2684 mm (for T = 0.1). Note that a quick literature research might suggest otherwise (some of our own Ionactive resource suggests 0.8 mm for the kVp and shielding material selected). This shows you, for a particular case, the TVT may be lower than expected.
Now look at this data from above: Next 1/10: Δ0.6265 mm → 0.895 mm. Note that the next TVT is not 0.2684 but is now 0.6265mm (much closer to the reported literature) - and the total (0.895 mm) is likely to be where T = 0.01. Pop 0.01 into the calculator and you will see the following:
- Required thickness
0.895 mm [as expected from results directly above] - Transmission used
1.000000e-2 (1 %) [as set by user T=0.01] - Analysis @ 100 kVp
Current thickness: 0.895 mm
Baseline: HVT₀ = 0.0489 mm · TVT₀ = 0.2684 mm
Next ½: Δ0.2419 mm → 1.1369 mm
Next 1/10: Δ0.8469 mm → 1.7419 mm [next 1/10 value - mm change required & new thickness]
Effective shielding: HVTs ≈ 6.644, TVTs ≈ 2.000
Material: Lead · kVp used: 100
Note from the above data that Next 1/10: Δ0.8469 mm is required for T=0.001, and that 0.8469 mm is close to the usual reported TVT for lead with 100kVp x-rays.
Some of the above might appear somewhat academic, especially when one considers the lead codes actually available for use- they can be found in this Ionactive resource: Lead shielding thickness - what are the lead codes?
Take a look at the first four codes.
Lead code | Lead (mm) | Weight (kg/m2) |
|---|---|---|
Code 3 | 1.32 | 15.0 |
Code 4 | 1.8 | 20.4 |
Code 5 | 2.24 | 25.4 |
Code 6 | 2.65 | 30.1 |
Using the calculator, we might wish to use code 4 (1.8 mm) if we require 0.1% (0.001) transmission (the calculator output is1.7419 mm).
Using a standard TVT of 0.8 mm (e.g. Ref: ASTM E 94 [2–4] ) could imply we need to use code 5 (2.24 mm) since 3 TVT is 2.4 mm. The difference does not seem a lot, but look at the kg/m3 values, that is a lot of additional lead. So this could be an overshielding issue.
[Ionactive comment: The above is provided to demonstrate the type of output and analysis from the calculator, and is not formal advice. As noted earlier, in some applications such as medical diagnostics, there is the real possibility of significant x-ray beam hardening, and a general safe bet would be to use a limiting TVT which can be found where the transmission-thickness curve becomes more linear. If you try T=0.0001 you will find Next 1/10: Δ0.9185 mm and 0.9 mm would be a safe bet. This will over design significantly in many circumstances, but probably not in the case of diagnostic x-ray with beam hardening. If in doubt always seek advice from a Radiation Protection Adviser (RPA).]
The calculator can also be used to demonstrate that density scaling between different shielding materials is a no no (!) when working with relatively low energy x-ray photons. With the calculator still set up as described above (but with transmission set back to T=0.1), we can see the following shielding choice comparisons for lead at 100 kVp.
- Lead - 0.2684 mm.
- Concrete (2.35 g/m3) - 25 mm.
- Gypsum - 77 mm.
- Steel - 1.8 mm.
- Plate glass - 31 mm.
- Wood - 306 mm.