How many rad is 1 sievert?

1 sievert equals exactly 100 rad when the radiation weighting factor (quality factor, Q) equals 1. This applies to gamma rays, X-rays, and beta particles. For higher-Q radiation (e.g. alpha particles, Q=20), the biological dose in sieverts is larger relative to the absorbed dose in rad.

What is the difference between sievert and rad?

The rad (radiation absorbed dose) measures energy deposited per unit mass of tissue: 1 rad = 0.01 J/kg. The sievert (Sv) is the SI unit of dose equivalent, which weights absorbed dose by the biological effectiveness of the radiation type. For Q=1 radiation, 1 Sv = 100 rad numerically.

Is this conversion always exactly 100?

Only when the quality factor Q = 1, which covers gamma rays, X-rays, and beta particles. For neutrons or alpha particles Q > 1, so 1 Sv corresponds to fewer rad (e.g. for alpha particles with Q=20, 1 Sv = 5 rad of alpha exposure, not 100 rad).

What is a millirem and how does it relate?

The rem (roentgen equivalent man) is the CGS counterpart of the sievert: 1 Sv = 100 rem, and 1 mSv = 100 mrem. One rad equals one rem for Q=1 radiation, so the rad/rem and gray/sievert pairs are numerically equivalent in that special case.

What is a safe radiation dose?

Typical background radiation is about 2–3 mSv/year (200–300 mrad/year). Occupational limits in most countries are 50 mSv/year (5 rad/year). A chest X-ray delivers roughly 0.1 mSv (10 mrad). Acute doses above 1 Sv (100 rad) can cause radiation sickness.

Sieverts to Rad Converter

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

Enter a dose in sieverts and instantly get the equivalent in rad, plus a reference table of common radiation dose levels.

Enter Dose in Sieverts

Sieverts (Sv)

Enter a value above to see the result.

Formula: rad = Sv × 100 — applies when quality factor Q = 1 (gamma, X-ray, beta).

Common Dose Reference

Exposure	Sv	Rad
Chest X-ray	0.0001 Sv	0.01 rad
CT scan (head)	0.001 Sv	0.1 rad
Annual background (avg)	0.0025 Sv	0.25 rad
CT scan (chest)	0.02 Sv	2 rad
Annual occupational limit	0.05 Sv	5 rad
Radiation sickness threshold	1 Sv	100 rad
LD50 (50% lethal dose)	4 Sv	400 rad
Near-certain fatality	10 Sv	1000 rad

Click any row to load that value into the converter.

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Summary

Enter a dose in sieverts and instantly get the equivalent in rad, plus a reference table of common radiation dose levels.

How it works

Enter the dose in sieverts (Sv, mSv, or any decimal) in the input field.
The converter multiplies your value by 100 to get rad.
The result updates instantly as you type.
Copy the result with one click.
Review the reference table to compare your result against common radiation exposures.

Use cases

Convert medical imaging dose reports from sieverts to rad for legacy systems.
Translate radiation safety limits between SI and CGS unit systems.
Cross-check occupational exposure records that use mixed unit conventions.
Verify textbook examples when studying nuclear physics or radiobiology.
Convert research data between sievert and rad for publication in older-format journals.
Compare dose readings from different radiation monitors using different unit systems.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu