Learn how to convert Grays per second (Gy/s) to Sieverts per second (Sv/s). Discover the conversion formula, radiation weighting factors (WR), and a quick reference table.

Gray/Second to Sievert/Second (Gy/s to Sv/s) Conversion Guide

Welcome to our professional resource for converting Grays per second (Gy/s) to Sieverts per second (Sv/s). In the fields of health physics, radiology, and nuclear safety, it is vital to distinguish between the physical energy absorbed by a material and the actual biological risk to human tissue. This page explains the relationship between these two units and how to calculate the equivalent dose rate.

Contextual Information: Physical vs. Biological Dose

To perform this conversion accurately, you must understand the difference between absorbed dose and equivalent dose:

• Gray (Gy): The SI unit of absorbed dose. It measures the physical energy (Joules) deposited by ionizing radiation into one kilogram of matter.
• Sievert (Sv): The SI unit of equivalent dose. It represents the biological effect or health risk of the radiation. It is calculated by taking the physical dose (Gray) and multiplying it by a “weighting factor” based on the type of radiation.
• Dose Rate: Expressed as “per second,” these units describe the intensity of the radiation field over time.

The Conversion Formula

The conversion from Grays per second to Sieverts per second is not always a 1:1 ratio. It depends entirely on the Radiation Weighting Factor (W_R), which accounts for the fact that some types of radiation are more damaging to living cells than others.

Formula:

Sv/s = Gy/s × W_R

Common Radiation Weighting Factors (W_R)

Depending on the source of radiation, you will use one of the following factors:

• Photons (X-rays and Gamma rays): W_R = 1
• Electrons and Muons (Beta particles): W_R = 1
• Protons and Charged Pions: W_R = 2
• Alpha particles, fission fragments, and heavy nuclei: W_R = 20
• Neutrons: Variable (typically between 5 and 20 depending on energy).

A Conversion Table (Quick Reference)

The table below shows common conversions for Photons and Electrons (W_R = 1), which are the most common in medical and industrial settings, versus Alpha Particles (W_R = 20).

Gray/Second (Gy/s)	Sv/s (Photons/Beta, WR=1)	Sv/s (Alpha, WR=20)
0.01 Gy/s	0.01 Sv/s	0.2 Sv/s
0.1 Gy/s	0.1 Sv/s	2 Sv/s
0.5 Gy/s	0.5 Sv/s	10 Sv/s
1 Gy/s	1 Sv/s	20 Sv/s
5 Gy/s	5 Sv/s	100 Sv/s
10 Gy/s	10 Sv/s	200 Sv/s

Importance of Equivalent Dose Rate

While the Gray per second tells us how much energy a machine is emitting or a material is absorbing, the Sievert per second is the critical measurement for human safety. For example, 1 Gray of Alpha radiation is 20 times more likely to cause biological damage (like DNA double-strand breaks) than 1 Gray of Gamma radiation. By applying the correct weighting factor, health physicists can determine stay times for workers in radiation zones and ensure that medical treatments remain within safe limits for healthy tissue.