Breast Cancer Risk Calculator
Use this breast cancer risk calculator to estimate your 5-year and lifetime chance of invasive breast cancer with the NCI Gail model.
Updated October 22, 2026
Medical Disclaimer: This calculator gives a general estimate for education only and cannot diagnose a condition. Share your result with your doctor or the clinician who ordered your test, and do not start, stop or change any medicine based on it. Read our full Medical Disclaimer.
How Breast Cancer Risk Is Calculated
Breast cancer risk here means absolute risk: the chance that a woman with your age and history will be diagnosed with invasive breast cancer within a set time. This calculator uses the Gail model behind the National Cancer Institute's Breast Cancer Risk Assessment Tool (BCRAT), which combines your answers with US cancer and death rates for your age and race or ethnicity.¹
What Breast Cancer Risk Measures
The result is a probability, not a diagnosis. It estimates how many women out of 100 with answers like yours would develop invasive breast cancer in the next 5 years and by age 90. It does not cover DCIS (an early, non-invasive form), and it cannot say whether you personally will get breast cancer.¹
The Formula
First the model builds your relative risk from your answers. Then it converts that into an absolute risk, year by year, allowing for the chance of dying from other causes first.
Relative risk = e^(b1 x biopsies + b2 x first period + b3 x first birth + b4 x relatives + b6 x first birth x relatives) x atypical hyperplasia factor, and from age 50 it is also multiplied by e^(b5 x biopsies)
Yearly breast cancer rate (h1) = baseline rate x (1 - attributable risk) x relative risk
Absolute risk = sum over each year of [h1 / (h1 + h2)] x S x (1 - e^-(h1 + h2))
Here h2 is the yearly death rate from other causes and S is the chance of reaching that year without either event. Gail and colleagues published the model in 1989.² NCI later added versions for Black, Asian and Pacific Islander, and Hispanic women.¹
How This Calculator Computes Your Result
Three screening questions come first. A past breast cancer, DCIS or LCIS, chest radiation, or a known BRCA1 or BRCA2 mutation stops the calculator.¹ You then enter your age (35 to 85), race or ethnicity (with birthplace for Hispanic women and a subgroup for Asian and Pacific Islander women), age at first period, age at first live birth, affected first-degree relatives, and any benign breast biopsies, including atypical hyperplasia.
Every coefficient and rate comes unchanged from the published BCRAT code (the BCRA R package). You see your 5-year and lifetime (to 90) risk, each next to the average for a woman of your age and race or ethnicity, rounded to one decimal place. "Unknown" answers count as the lowest-risk option, which can make your result an underestimate.
What Your Result Means
Result shown | What it tells you |
5-year risk | Your chance of invasive breast cancer in the next 5 years |
Lifetime risk (to 90) | Your chance of invasive breast cancer by age 90 |
Average risk | The same figure for a woman of your age and race or ethnicity |
Lower than average | Your risk is under 0.9 times the average |
About average | Your risk is 0.9 to 1.1 times the average |
Higher than average | Your risk is over 1.1 times the average |
For example, a 40-year-old White woman with one benign biopsy (no atypical hyperplasia), a first period at 12, a first birth at 25 to 29 and one affected relative gets a 5-year risk of 1.7% against an average of 0.6%, and a lifetime risk of 22.6% against 12.4%. The lowest-risk answers can give a below-average result: a 60-year-old White woman with none of these factors gets 0.9% against 1.8%.
How Each Answer Changes Your Risk
In the model for White women, these are the multipliers your answers add to your relative risk.²
Answer | Multiplier |
First period at 12 to 13 / at 11 or younger | 1.10 / 1.21 |
First birth at 20 to 24 / 25 to 29 or no births / 30 or older | 1.24 / 1.55 / 1.93 |
One affected relative (first birth under 20 / 30 or older) | 2.61 / 1.47 |
Two or more affected relatives (first birth under 20 / 30 or older) | 6.80 / 2.16 |
One benign biopsy (under 50 / 50 and over) | 1.70 / 1.27 |
Two or more biopsies (under 50 / 50 and over) | 2.88 / 1.62 |
Biopsy with no atypical hyperplasia found | 0.93 |
Atypical hyperplasia on a biopsy | 1.82 |
Family history has the largest effect, and it shrinks when the first birth came later. Other groups use their own coefficients; for Black women, age at first birth is not in the model.¹
Who Should Use a Different Tool
NCI says the tool cannot accurately estimate risk after breast cancer, DCIS, LCIS or chest radiation, or with a BRCA1 or BRCA2 mutation, and it points mutation carriers to CanRisk.¹ The Gail model also ignores second-degree relatives, relatives' age at diagnosis, ovarian cancer and male breast cancer. With a strong family history, models built on detailed family history, such as Tyrer-Cuzick (IBIS) or CanRisk, usually fit better.
How the Result Is Used in Practice
The US Preventive Services Task Force (USPSTF) recommends mammograms every 2 years from 40 to 74, including women with some added risk factors, but not people with a high-risk genetic marker or past breast cancer.⁵ On risk-reducing medicines, it says there is no single cutoff for increased risk. Trials most often enrolled women with a Gail 5-year risk above 1.66%, and women at 3% or more are more likely to benefit than be harmed.⁴ For women 35 and older at increased risk and low risk of side effects, it recommends that clinicians offer medicines such as tamoxifen, raloxifene or aromatase inhibitors, and it recommends against routine use in women not at increased risk.⁴ The American Cancer Society's yearly MRI advice, for a lifetime risk of about 20% to 25% or more, relies on tools based mainly on family history, which the Gail model is not.⁶
How Each Answer Multiplies Relative Risk
The multipliers in the Gail model for White women. A larger number raises your relative risk more.
Show data table
| Answer | Multiplier |
|---|---|
| First period at 12 to 13 | 1.10 |
| First period at 11 or younger | 1.21 |
| First birth at 20 to 24 | 1.24 |
| First birth at 25 to 29, or no births | 1.55 |
| First birth at 30 or older | 1.93 |
A Note on Accuracy
In US women, the Gail model predicts the number of cancers in a group well (expected to observed ratio about 0.98) but is weak at telling which woman will get cancer (AUC about 0.61, where 0.5 is a coin toss).³ The USPSTF puts most risk models at 0.55 to 0.65.⁴ NCI notes it may underestimate risk in Black women with previous biopsies and in Hispanic women born outside the US, and that estimates for American Indian or Alaska Native women rest partly on data for White women.¹ It leaves out breast density, alcohol, body weight, hormone therapy and genetic test results, so treat the number as a starting point, not a forecast.
Frequently Asked Questions
What is a normal Gail model score?
There is no single normal score, because average risk rises with age. In this model the average 5-year risk for a White woman is about 0.6% at 40 and 1.8% at 60, and the USPSTF notes that trials most often used 1.66% as the cutoff for increased risk.⁴
How accurate is the Gail model?
It predicts how many women in a large group will get breast cancer quite well, but it is only modestly better than chance at telling which individual woman will.³
What is the average lifetime risk of breast cancer?
In this model, an average 35-year-old White woman has about a 12.6% chance of invasive breast cancer by age 90, roughly 1 in 8.
Can I use this calculator if breast cancer runs in my family?
Only if you have no known BRCA mutation, and it counts only mothers, sisters and daughters. With a strong family history, Tyrer-Cuzick or CanRisk usually gives a better estimate.¹
Sources
Breast Cancer Risk Assessment Tool: About the Tool, National Cancer Institute
Projecting Individualized Probabilities of Developing Breast Cancer, Gail et al., 1989
Assessment of Performance of the Gail Model, Wang et al., 2018
Breast Cancer: Medication Use to Reduce Risk, USPSTF, 2019
Breast Cancer: Screening, USPSTF, 2024
Recommendations for the Early Detection of Breast Cancer, American Cancer Society