Radiation Dose Calculator: Compare Your Medical Scans

Quick answer: Use the calculator below to add up the approximate radiation from the scans you’ve had, such as CT scans, X-rays, mammograms and PET/CT. It shows your total in millisieverts (mSv) and compares it with natural background radiation, chest X-rays and coast-to-coast flights. The numbers are typical estimates for an average adult, not your exact personal dose, and they don’t predict your cancer risk.

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<p class="rdc-title">Radiation Dose Calculator</p>
<p class="rdc-sub">Add the scans you've had to see their approximate total radiation dose and how it compares with natural background radiation, X-rays and flights.</p>

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<p class="rdc-empty" id="rdc-empty">No scans added yet.</p>

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<p class="rdc-result-label">Approximate total effective dose</p>
<p class="rdc-result-value" id="rdc-total">0 mSv</p>
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<p class="rdc-note">Educational estimate only. Values are typical effective doses for an average-sized adult from RadiologyInfo.org. Your actual dose depends on your body size, the scanner and the protocol, and can be several times higher or lower. This tool does not estimate your personal cancer risk and is not medical advice. Never avoid a scan your doctor says you need because of this number; talk to your doctor instead.</p>
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How to use the calculator

Choose an exam from the list. Pick the closest match to what you had.
Enter how many times you’ve had it, then press Add.
Repeat for your other scans. To remove one, press the × next to it.
Read your total and the comparisons below it.

Not sure which scans you’ve had? Your patient portal usually lists your imaging history, or you can ask your doctor’s office or the imaging center.

The doses behind the calculator

The calculator uses typical effective doses for an average-sized adult published by RadiologyInfo.org, from the American College of Radiology and the Radiological Society of North America.

Exam	Typical dose (mSv)
X-ray of hand, foot or other limb	0.001
DEXA bone density scan	0.001
Dental X-ray (bitewing)	0.005
Panoramic dental X-ray	0.025
Chest X-ray	0.1
Screening mammogram (2D)	0.28
3D mammogram	0.34
CT head and neck	1.2
Low-dose CT lung screening	1.5
CT head (brain)	1.6
Coronary calcium score CT	1.7
CT colonography	6
CT chest	6.1
CT abdomen and pelvis	7.7
Coronary CT angiography	8.7
CT spine	8.8
PET/CT, whole body	22.7
MRI and ultrasound	0 (no ionizing radiation)

The comparisons use about 3 mSv a year of natural background radiation in the U.S., 0.1 mSv for a chest X-ray and about 0.035 mSv for a coast-to-coast U.S. flight.

How to read your result

Under about 1 mSv: less than a few months of natural background radiation. Most X-rays, dental X-rays, mammograms and DEXA scans fall here.
About 1 to 10 mSv: similar to several months to a few years of natural background radiation. Most single CT scans are in this range.
Above about 10 mSv: common for people who’ve had several CT scans or a PET/CT, for example during cancer care. It’s a reason to keep track of your imaging and to make sure each new scan is needed, not a reason to refuse one.

These bands are a simple guide to put numbers in context, not medical categories.

What the calculator can’t tell you

Your exact dose. Real doses depend on your body size, the scanner, the protocol and the reason for the scan, and can be several times higher or lower than the typical value.
Your personal cancer risk. Risk estimates at these doses are uncertain and depend on age, sex and the organs exposed. A single number would be misleading, so the calculator doesn’t give one. If you’re worried, talk to your doctor.
Whether a scan is worth it. That depends on what the scan can find. When a CT or PET/CT is needed, the benefit of the right diagnosis almost always outweighs the small radiation risk.

When keeping track is most useful

You’re having regular CT or PET/CT scans, for example cancer surveillance.
You’ve had several CT scans in a short time, such as after an injury.
You’re switching doctors or hospitals and want to avoid repeat scans.
You’re a parent keeping track of a child’s imaging.

In these cases, share your imaging history with your doctor, and ask whether lower-dose options or MRI or ultrasound could answer the same question.

From the scanner room

[TU EXPERIENCIA: qué preguntan los pacientes con muchos TC o PET de seguimiento sobre la dosis acumulada; cómo les explicas que la dosis real depende del protocolo; si tu centro registra la dosis de cada estudio (dose report, registro de dosis).]

Tips from the technologist

Ask for your dose report. Many CT scanners record the dose of each exam. Some centers can share it or include it in your record.
Bring your prior images and reports. It helps avoid repeat scans and lets the radiologist compare.
Tell us if you might be pregnant, and always mention it before any scan of the abdomen or pelvis.
Don’t skip a needed scan to keep your number low. A delayed diagnosis is usually a bigger risk than the radiation.

FAQ

How much radiation is too much from medical scans?

There’s no fixed limit for patients, because each scan should be justified by its medical benefit. What matters is that every scan is needed and uses the lowest dose that gives a good answer.

Is this calculator accurate?

It gives typical values, which is useful for comparison. Your real dose for any scan can be quite different. For an exact figure, ask the imaging center for your dose report.

Why doesn’t the calculator show a cancer risk?

Because personal risk at these doses can’t be estimated reliably from a single number, and a misleading figure could cause unnecessary worry or lead someone to skip a scan they need.

Do MRI and ultrasound count?

No. They don’t use ionizing radiation, so they add 0 mSv.

How much radiation do we get naturally each year?

About 3 mSv a year on average in the U.S., mostly from radon in homes, plus cosmic rays, the ground and our own bodies.

This calculator and article are for general information only and are not medical advice. Talk to your doctor about the benefits and risks of any imaging test.

Sources

RadiologyInfo.org (ACR/RSNA). Radiation Dose in X-Ray and CT Exams.
FDA. What Are the Radiation Risks from CT?
Health Physics Society. What radiation doses do people receive from flying commercially?
Image Gently Alliance. Information for parents.
ACR. Dose Index Registry.