What is the relationship between rad and gray?

1 rad equals exactly 0.01 gray (Gy). The rad is the CGS unit of absorbed radiation dose, while the gray is the SI unit. The gray replaced the rad in the international system; 1 Gy = 100 rad.

When would I use rad instead of gray?

The rad is still common in older American medical and nuclear literature. The gray is the modern SI standard and is used in most current international publications, regulatory documents, and medical physics practice.

Is gray the same as sievert?

No. Both measure radiation, but gray (Gy) measures absorbed dose (energy deposited per kilogram of tissue), while sievert (Sv) measures effective dose, which weights absorbed dose by radiation type and tissue sensitivity. For X-rays and gamma rays, 1 Gy numerically equals 1 Sv, but they are different quantities.

What dose in gray is considered dangerous?

Whole-body doses above 1 Gy can cause acute radiation syndrome. Doses above 4–5 Gy without medical treatment are potentially lethal. In therapeutic oncology, localized doses of 40–80 Gy to a tumor are common, delivered in fractions to spare surrounding tissue.

Can I convert millirad to milligray with this tool?

Yes. The 0.01 factor applies regardless of prefix. 1 millirad = 0.01 milligray. Simply enter your millirad value and the result is in milligray.

Rad to Grays Converter

Name: Rad to Grays Converter
Availability: InStock
Author: Nham Vu

Convert rad to gray (Gy): enter a value in rad and get the equivalent in gray instantly.

Enter Dose in Rad

Rad (rad)

Result in Gray (Gy)

Enter a value on the left to see the result

Common Rad to Gray Conversions

Rad (rad)	Gray (Gy)	Context
0.001	0.00001	1 millirad (background level)
1	0.01	1 rad = 10 milligray
10	0.1	100 milligray
100	1	1 Gy — low-level therapy dose
500	5	~LD50 whole-body dose
6000	60	Typical tumor treatment course

Summary

Convert rad to gray (Gy): enter a value in rad and get the equivalent in gray instantly.

How it works

Enter a dose value in rad in the input field.
The converter multiplies your value by 0.01 to get grays (1 rad = 0.01 Gy).
The result in gray (Gy) appears instantly below the input.
Use the swap button to convert in the reverse direction (Gy to rad).
Copy the result to clipboard with one click.

Use cases

Convert historical radiation dose records from rad to SI units (Gy).
Cross-check absorbed dose calculations in radiation oncology treatment planning.
Translate radiation safety thresholds between CGS and SI unit systems.
Verify dose values when reviewing older medical physics literature.
Convert dosimeter readings for radiation protection compliance reports.
Support educational exercises in nuclear medicine and health physics courses.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu