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X-ray Exposure Time Calculator

X-ray Exposure Time Calculator

Input your X-ray tube parameters, material, and film setup to calculate estimated exposure times. Use the dual timers for single or double film techniques.

mA
mm

Calculated Exposure Time

00:00:00

Single Film Timer

Spacer

00:00

Double Film Timer

Typically +10-20% time if superimposed

00:00

Recent Exposures

Tube Setup Time Action

X-ray Exposure Formula

Unlike Gamma, X-ray calculates required Exposure (mA·min) using empirical base values, adjusting for distance and material attenuation before dividing by tube current.

Time = [ E_base * F * (SFD/1000)² * 2^(x/HVL) ] / mA

  • E_base: Base exposure required for the chosen kV (at 1000mm)
  • F: Film & Density Factor
  • SFD: Source to Film Distance in mm
  • x: Material Thickness
  • HVL: Half Value Layer (depends on kV)
  • mA: Tube Current
Current Calculation:
T = [ * * (/1000)² * 2^( / ) ] /
= mins

X-ray Parameters

Understanding the electrical variables of the X-ray tube allows fine-tuning of contrast and exposure speed.

  • Tube Voltage (kV): Controls the quality or penetrating power of the beam. Higher kV increases penetration (higher HVL) and reduces exposure time drastically, but lowers image contrast.
  • Tube Current (mA): Controls the quantity or intensity of radiation. Exposure time is inversely proportional to mA. (e.g., Doubling the mA halves the time).
  • Material Attenuation: Because X-rays are a spectrum of energies (bremsstrahlung), the HVL changes as the beam hardens through thicker materials. This calculator uses standard effective HVL approximations.
Disclaimer: This calculator provides estimated X-ray exposure times based on empirical formulas and standard film factors. Actual exposure charts vary significantly between different X-ray tube manufacturers, window materials, and focal spot sizes. Always verify against the specific exposure charts provided for your equipment.

Approximate X-ray HVL (mm)

Unlike Gamma isotopes which have discrete energies, X-ray HVL depends on the applied Tube Voltage (kV). These are standard educational approximations.

Material 100 kV 150 kV 200 kV 250 kV 300 kV
Steel 1.0 1.5 2.5 3.2 4.0
Aluminum 4.0 6.0 9.0 12.0 16.0

X-ray Film Equivalency

Standard Equivalency (ISO 11699-1)

ClassAgfa StructurixCarestream IndustrexFujifilm IXMultiplier
C1-C2D3M100IX251.50
C3D4MX125IX501.00 (Base)
C4D5T200IX800.60
C5D7AA400IX1000.35
C6D8HS800IX1500.15

Density Multipliers

Relative exposure required to hit specific optical densities.

D 1.5 = x0.6 D 2.0 = x1.0 D 2.5 = x1.5 D 3.0 = x2.2 D 3.5 = x3.2 D 4.0 = x4.5

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