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Radiation Dose Converter

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Absorbed Dose Conversion

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Common Conversions

Absorbed Dose

1 Gy = 100 rad

Absorbed Dose

10 mGy = 1 rad

Equivalent Dose

1 mSv = 100 mrem

Exposure

1 R = 2.58×10⁻⁴ C/kg

About This Tool

Radiation Dose Converter – Gy, Sv, Rad, Rem, Roentgen and More

The Radiation Dose Converter lets you instantly convert between all common radiation dose and exposure units used in medical imaging, nuclear medicine, radiation protection, and physics research. It covers three independent measurement categories: absorbed dose, equivalent dose, and radiation exposure — with support for both modern SI units and the traditional units still widely used in clinical and regulatory practice.

The Three Dose Quantity Categories

Radiation dose is not a single concept. Physicists and health professionals use three distinct quantities, each measured in different units that cannot be freely intermixed without additional information:

  • Absorbed Dose — the energy deposited per kilogram of material by ionising radiation, regardless of radiation type. The SI unit is the Gray (Gy); the traditional unit is the rad (1 Gy = 100 rad). Milligray (mGy), microgray (µGy), and kilogray (kGy) are also commonly used.
  • Equivalent Dose — the absorbed dose weighted by the biological effectiveness of the radiation type. The SI unit is the Sievert (Sv); the traditional unit is the rem (1 Sv = 100 rem). Millisievert (mSv), microsievert (µSv), and millirem (mrem) appear frequently in occupational health and public-dose contexts.
  • Exposure — the ionisation charge produced in dry air by X-rays or gamma radiation. The SI unit is Coulombs per kilogram (C/kg); the traditional unit is the Roentgen (R) (1 R = 2.58 × 10⁻⁴ C/kg, exact). Milliroentgen (mR) is common in environmental monitoring.

How the Conversion Works

All conversions use a two-step normalisation approach. Every unit is defined by its factor relative to the SI base unit of its category. To convert from unit A to unit B:

  1. Multiply the input value by the factor that converts unit A to the base unit (e.g., 1 mGy × 0.001 = 0.001 Gy).
  2. Divide the base-unit value by the factor for unit B (e.g., 0.001 Gy ÷ 0.01 = 0.1 rad).

This gives a result of 1 mGy = 0.1 rad, which matches the known relationship. The same pattern applies across all three categories.

Key Conversion Reference

The most frequently needed exact relationships are:

  • 1 Gy = 100 rad (exact)
  • 1 Sv = 100 rem (exact)
  • 1 mSv = 100 mrem (exact)
  • 1 R = 2.58 × 10⁻⁴ C/kg (exact, NIST definition)
  • 1 cGy = 1 rad — a common equivalence used in radiotherapy planning

Why Absorbed Dose and Equivalent Dose Cannot Be Directly Converted

For X-rays, gamma rays, and electrons, the radiation weighting factor wR = 1, so numerically 1 Gy equals 1 Sv. However, for alpha particles (wR = 20) and fast neutrons (wR up to 20), the equivalent dose is much higher than the absorbed dose. Because the weighting factor depends on radiation type and energy — not a fixed constant — a simple unit converter cannot perform this cross-category conversion. Each category is kept independent in this tool.

Typical Dose Values for Context

Understanding the scale of your converted result is easier with reference points. The global average annual background radiation dose is approximately 2.4 mSv (240 mrem). A chest X-ray delivers roughly 0.1 mSv; a chest CT scan approximately 5–10 mSv. The ICRP-recommended occupational dose limit for radiation workers is 20 mSv per year (averaged over five years). Acute whole-body doses above 1 Sv may cause radiation sickness; doses above approximately 4 Sv are potentially lethal without medical treatment.

Practical Use Cases

This tool is used by medical physicists converting between SI and legacy units for treatment planning, radiologists comparing CT dose index values,radiation protection officers checking occupational dose limits expressed in rem against international mSv standards, and students working through textbook problems that mix unit systems. The precision selector (0–10 decimal places) accommodates both quick estimates and high-accuracy scientific work.

Using the Tool

Select a dose category using the tabs at the top of the tool: Absorbed Dose, Equivalent Dose, or Exposure. Enter the numeric value, choose the source and target units from the drop-down menus, and the result updates immediately. Enable the “Show all unit conversions” toggle to see your input expressed in every unit of the selected category at once — useful for at-a-glance comparisons. The Swap button reverses the conversion direction, and Copy Result copies the output to the clipboard.

Frequently Asked Questions

Is the Radiation Dose Converter free?

Yes, Radiation Dose Converter is totally free :)

Can I use the Radiation Dose Converter offline?

Yes, you can install the webapp as PWA.

Is it safe to use Radiation Dose Converter?

Yes, any data related to Radiation Dose Converter only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does this radiation dose converter work?

The tool converts values within three independent dose categories: Absorbed Dose, Equivalent Dose, and Exposure. Within each category, every conversion normalizes through an SI base unit — Gray (Gy) for absorbed dose, Sievert (Sv) for equivalent dose, and Coulomb per kilogram (C/kg) for exposure. The input value is multiplied by the source unit's conversion factor to reach the base unit, then divided by the target unit's factor to produce the final result.

What is the difference between absorbed dose and equivalent dose?

Absorbed dose (measured in Gray or rad) describes the physical energy deposited per kilogram of matter by ionising radiation — it is independent of radiation type. Equivalent dose (measured in Sievert or rem) multiplies the absorbed dose by a radiation weighting factor (wR) that reflects the relative biological effectiveness of the radiation. For X-rays and gamma rays, wR = 1 so 1 Gy = 1 Sv; for alpha particles, wR = 20 so the same absorbed energy causes 20 times more biological damage.

What is the Roentgen, and how does it relate to modern exposure units?

The Roentgen (R) is a legacy unit measuring ionisation produced in air by X-rays or gamma rays. It is defined as the charge produced per unit mass of dry air: 1 R = 2.58 × 10⁻⁴ C/kg (exact, by NIST definition). The SI replacement is the Coulomb per kilogram (C/kg), which covers the same physical quantity without the historical dimensional constraints.

Why can't I convert between absorbed dose and equivalent dose here?

Converting from absorbed dose (Gy) to equivalent dose (Sv) requires knowing the radiation weighting factor (wR), which depends on the type and energy of the radiation — it is 1 for photons and electrons, but 20 for alpha particles and up to 20 for fast neutrons. Because that factor is not a fixed constant, the conversion cannot be done with a simple unit converter. For photon and electron radiation specifically, 1 Gy equals 1 Sv numerically.

What radiation doses are considered safe or dangerous?

The global average annual background dose is approximately 2.4 mSv. The ICRP-recommended occupational dose limit is 20 mSv per year (averaged over five years). Acute whole-body doses above roughly 1 Sv can cause radiation sickness, and above 4 Sv the untreated 50% lethal dose threshold (LD50) is approached. A chest X-ray delivers about 0.1 mSv; a CT scan roughly 5–10 mSv. This tool is for unit conversion only and does not constitute medical or radiation safety advice.

Are the conversion results accurate for professional use?

Yes. All conversion factors are based on exact SI definitions: 1 rad = 0.01 Gy (exact), 1 rem = 0.01 Sv (exact), 1 R = 2.58 × 10⁻⁴ C/kg (exact). Calculations use IEEE 754 double-precision floating-point arithmetic (approximately 15 significant digits of precision). For regulatory submissions, always verify against the applicable standards of your jurisdiction.