A good coronary calcium score is zero. A score of zero means no detectable calcium buildup in your coronary arteries, and it carries less than a 1% risk of heart attack or stroke over the next 10 years. Among people with stable chest pain, a zero score corresponds to roughly a 0.5% annual rate of major cardiac events. Any score above zero indicates some degree of plaque in the arteries, but low scores still represent relatively low risk.
How the Scoring System Works
A coronary calcium scan uses a CT scanner to detect calcified plaque in the arteries that supply your heart. The result is reported as an Agatston score, named after the cardiologist who developed the method. The score reflects both the amount and density of calcium deposits. Higher numbers mean more plaque buildup, which correlates with higher cardiovascular risk.
The standard risk categories break down like this:
- 0: Very low risk. Less than 1% chance of heart attack or stroke over 10 years.
- 1 to 100: Low risk. Less than 10% chance over 10 years.
- 101 to 400: Moderate risk. 10 to 20% chance over 10 years.
- Over 400: High risk. Greater than 20% chance over 10 years.
Within the moderate category, people whose score falls above the 75th percentile for their age and sex face risk closer to 15 to 20%. That percentile comparison matters because a score of 150 means something very different for a 45-year-old woman than for a 75-year-old man.
Why a Zero Score Is So Reassuring
A zero calcium score is sometimes called the “negative risk factor” because it’s one of the strongest predictors of a low likelihood of cardiac events. Even in people who have chest pain, a zero score predicts a very low rate of serious problems. This makes it a powerful tool for avoiding unnecessary invasive testing or treatments. If your score is zero and you’re otherwise at low or borderline risk, you’re unlikely to benefit from cholesterol-lowering medication or daily aspirin.
That said, a zero score isn’t a lifetime guarantee. Plaque can develop over time, and some early plaque is “soft” (not yet calcified), which a calcium scan won’t detect. For most people with a zero score, the reassurance holds for roughly five to ten years before a repeat scan might be worth considering.
What Your Score Means for Treatment
Calcium scores directly influence whether your doctor recommends starting a statin or aspirin. The 2019 ACC/AHA prevention guidelines recommend using the calcium score to guide decisions for people at intermediate cardiovascular risk, particularly when there’s uncertainty about whether statin therapy is warranted.
A score of zero generally tips the scale against starting a statin for primary prevention. Aspirin for heart attack prevention is also not recommended at zero, because the bleeding risk outweighs any cardiovascular benefit. Once the score reaches 100 or higher, the calculus shifts. At that point, aspirin’s cardiovascular benefit tends to outweigh its bleeding risk, and more aggressive cholesterol management becomes appropriate. At 300 or above, the risk of heart attack approaches that of someone who has already had one, so high-intensity statin therapy and aspirin are typically both considered.
Your Age, Sex, and Ethnicity Matter
A raw Agatston score only tells part of the story. What counts as “good” depends heavily on how your score compares to other people your age, sex, and racial or ethnic background. The Multi-Ethnic Study of Atherosclerosis (MESA) established percentile tables that put individual scores in context.
Calcium scores rise naturally with age, and men accumulate calcium faster than women. Among white men aged 65 to 74, the median (50th percentile) score is 145. For white women in the same age range, the median is just 13. A score of 100 in a 50-year-old man would place him well above the 75th percentile, flagging elevated risk. The same score in a 78-year-old man could fall below average.
Ethnicity creates significant differences as well. White men consistently have the highest calcium scores at every age. Chinese American men have the lowest scores at older ages, with 75th percentile values roughly one-quarter of those for white men in the 75 to 84 age group. Among women, the pattern is similar: white women tend to have the highest scores, while Hispanic and Chinese American women tend to have the lowest. These differences reflect a combination of genetics, dietary patterns, and other risk factors, and they’re the reason most cardiologists look at your percentile ranking, not just the raw number.
How Scores Change Over Time
Coronary calcium scores don’t go down. Once calcium is deposited, it stays. But the rate at which your score increases matters enormously. In people taking statins, the average annual increase is about 17%. Those who went on to have a heart attack showed an average yearly increase of 42%, more than double the rate of people who stayed event-free. Historical data from people not on statins showed an even steeper average increase of 52% per year.
A yearly increase of 15% or more is considered a meaningful progression, and it’s one of the strongest predictors of future heart attack. People whose scores grew at that pace had a 17-fold higher risk of heart attack compared to those with slower or no progression. When rapid progression was combined with a high baseline score (over 400), the risk multiplied further. Event-free survival was 97% in people without rapid progression, compared to just 66% in those whose scores climbed 15% or more per year.
This is why some cardiologists recommend repeat calcium scoring every five to seven years for people with non-zero scores. Tracking the trajectory can be more informative than any single snapshot.
Volume and Density Tell a Deeper Story
The standard Agatston score combines two properties of plaque: how much of it there is (volume) and how dense the calcium deposits are. Research from the MESA study found that these two components actually pull cardiovascular risk in opposite directions. Greater plaque volume increases risk, as you’d expect. But denser calcium is associated with lower risk. Each standard-deviation increase in calcium density corresponded to a 25 to 28% reduction in cardiovascular events.
Dense, calcified plaque is thought to be more stable and less likely to rupture, which is the event that triggers most heart attacks. Softer, less calcified plaque is more vulnerable. This means two people with identical Agatston scores can have meaningfully different risk profiles depending on whether their plaque is large and diffuse or small and dense. The standard Agatston score doesn’t separate these components, though newer research suggests that reporting volume and density individually improves risk prediction. Most routine scan reports still use the Agatston score alone, but this is an area where interpretation is evolving.
Who Should Get a Calcium Score
Calcium scoring is most useful for people at borderline or intermediate 10-year cardiovascular risk, typically estimated at 5 to 20%. These are people where the decision to start preventive medication could go either way. A zero score can provide reassurance and a reason to hold off on statins. A high score can provide the motivation to start treatment aggressively.
The test is less useful at the extremes. If you’re already at high risk due to very high cholesterol, diabetes, or a prior cardiovascular event, you’ll likely need treatment regardless of your calcium score. If you’re young with no risk factors, the test is unlikely to show anything actionable. The scan involves a small amount of radiation (comparable to a mammogram) and typically costs $75 to $300 out of pocket, since many insurance plans don’t cover it for screening purposes.