Radiation Converter — Gy/rad, Sv/rem and Bq/Ci

Background.

Radiation measurements use several units that look convertible but describe different physical quantities. Activity counts nuclear transformations, absorbed dose measures energy deposited per mass, and equivalent dose applies radiation-weighting concepts to dose. Confusing them is not a harmless unit mistake, so this calculator begins by making the quantity explicit.

Choose absorbed dose to convert gray, milligray, microgray and rad. One gray is one joule deposited per kilogram, and one rad is exactly 0.01 Gy. These units say how much energy a material absorbed; they do not by themselves state a biological risk.

Choose equivalent dose to convert sievert, millisievert, microsievert and rem. One rem is exactly 0.01 Sv. Although gray and sievert share the base dimension J/kg, BIPM gives them different special names because they identify different quantities and confusing them can endanger health. This page never offers Gy-to-Sv conversion.

Choose radioactivity to convert becquerel and curie families. One becquerel is one nuclear transformation per second. One curie is exactly 37 billion becquerels, so one millicurie is 37 MBq and one microcurie is 37 kBq. Activity does not determine a person's dose without radionuclide, emissions, geometry, time, shielding and biological information.

The selected quantity controls which units are valid. If absorbed dose is selected and a sievert or becquerel unit is chosen, the calculator returns a field-specific error instead of manufacturing a number. This dimensional gate is the most important part of the page. Always retain the quantity name beside the number when copying a result into another record or calculation.

The worked example converts 250 mGy to 0.25 Gy and 25 rad. It remains absorbed dose throughout. Relabelling 25 rad as 25 rem would require a defined dose-equivalent model and weighting factors that are outside a unit conversion.

Values must be finite and non-negative. Decimal.js carries every exact factor, and the converted and SI values round once at ten decimal places. A plain-language statement repeats the source and target units so the result cannot be read without its quantity context.

This page deliberately excludes roentgen. Roentgen measures exposure through ionisation in air, not activity, absorbed dose or equivalent dose. Approximate practical relationships sometimes printed between roentgen, rad and rem depend on radiation type, energy and medium and are not universal identities.

No result here is a safety verdict, clinical interpretation or regulatory limit. Medical exposure questions need a clinician or medical physicist. Workplace and facility decisions must follow the applicable licensed radiation-protection programme and regulator. The converter changes notation only.

What is radiation unit converter?

Radiation units belong to different quantities. Becquerel and curie measure activity, gray and rad measure absorbed dose, and sievert and rem measure dose equivalent. Conversion is valid only within one row. Shared base dimensions do not make gray and sievert interchangeable.

How to use this calculator.

1. 01Identify whether the source value is activity, absorbed dose or equivalent dose.
2. 02Choose that quantity before selecting source and target units.
3. 03Enter a non-negative value and keep both units within the chosen quantity.
4. 04Read the SI value and repeated quantity label as cross-checks.
5. 05Do not use the result as medical advice, a risk estimate or a regulatory-compliance decision.

The formula.

Each quantity has its own SI base and factor table. Absorbed dose normalises to gray, equivalent dose to sievert, and activity to becquerel. Source and target must exist in the same table. Multiply by the source factor and divide by the target factor.

For 250 mGy, SI absorbed dose is 250×0.001 = 0.25 Gy. Divide by 0.01 Gy/rad to obtain 25 rad. Decimal.js carries the arithmetic and rounds once at the output boundary.

A worked example.

Frequently asked questions.

References& sources.

1. [1]NIST SP 811 Appendix B.9 supplies rad-to-gray, rem-to-sievert and curie-to-becquerel factors.
2. [2]U.S. NRC 10 CFR Part 20 §§20.1004–20.1005 independently defines dose and activity units.
3. [3]BIPM SI Brochure assigns distinct special names to becquerel, gray and sievert to prevent quantity errors.