Breast Cancer Risk Estimator
Simplified educational adaptation of the Gail model — not the clinical BCRAT. Estimate 5-year and lifetime risk of developing invasive breast cancer from six classic risk factors.
Before you start — eligibility
The Gail model was not designed for the groups below. If either applies, the tool will not produce a number.
Your estimated risk
5-year risk of developing invasive breast cancer in the next 5 years
Lifetime risk (to age 90)
Compared with an average woman your age
How your factors combine
| Factor | Your answer | Relative risk |
|---|---|---|
| Combined relative risk (multiplied) | ||
Relative risks from Gail et al., JNCI 1989. See Methodology below for full sources and simplifications.
Methodology — what this calculator does
The formula
Each factor contributes a relative risk (RR). They are multiplied:
RRtotal = RRmenarche × RRfirst birth × RRrelatives × RRbiopsies × RRhyperplasia
5-year risk ≈ 1 − exp(−baseline × RRtotal × 5), where baseline is the approximate annual incidence for your 5-year age group (table below).
Lifetime risk (to age 90) sums risk across future 5-year age bands with a simple competing-mortality adjustment (DevCan-style): for each band, cancer probability = (h/(h+m)) × (1 − exp(−(h+m)×5)), weighted by the probability of surviving cancer-free to that band. h = baseline × RR, m = all-cause mortality.
Relative risks used (source: Gail et al., JNCI 1989, Table 3)
| Factor | Category | RR |
|---|---|---|
| Age at menarche | < 12 | 1.21 |
| 12–13 | 1.10 | |
| ≥ 14 | 1.00 | |
| Age at first live birth | < 20 | 1.00 |
| 20–24 | 1.24 | |
| 25–29 | 1.59 | |
| ≥ 30 | 1.93 | |
| No live births | 1.93 | |
| First-degree relatives | 0 | 1.00 |
| 1 | 2.61 | |
| ≥ 2 | 6.80 | |
| Breast biopsies | 0 | 1.00 |
| 1 | 1.70 | |
| ≥ 2 | 2.88 | |
| Atypical hyperplasia | Yes (only if biopsied) | 1.82 |
Sources: Gail MH, Brinton LA, Byar DP, et al. “Projecting individualized probabilities of developing breast cancer for white females who are being examined annually.” J Natl Cancer Inst. 1989;81(24):1879–1886 (relative risks). Updated clinical model (BCRAT): Costantino JP, Gail MH, et al., JNCI 1999. The 1.82 hyperplasia multiplier is a simplified approximation of the biopsy–hyperplasia interaction in Gail 1989.
Baseline incidence by age (source: approximate, based on published NCI SEER data)
| Age group | New cases / 100,000 / year (approx) |
|---|---|
| 35–39 | 60 |
| 40–44 | 120 |
| 45–49 | 190 |
| 50–54 | 230 |
| 55–59 | 275 |
| 60–64 | 335 |
| 65–69 | 395 |
| 70–74 | 430 |
| 75–79 | 440 |
| 80–84 | 425 |
| 85–89 | 375 |
Rounded educational approximations consistent with published NCI Surveillance, Epidemiology, and End Results (SEER) age-specific female breast cancer incidence. Not an exact reproduction of any single SEER release. Competing mortality uses approximate US life-table all-cause rates (35–39: 0.14%/yr … 85–89: 14.5%/yr).
Honest limitations (read before trusting a number)
- Not the clinical BCRAT. The clinical tool calibrates its baseline to the lowest-risk reference group using population attributable risk; this version multiplies onto population-average SEER rates, which can overestimate risk for low-risk profiles and misstate extreme factor combinations.
- No age interactions, no race/ethnicity adjustment. The original Gail estimates came mainly from white women in the BCDDP screening program; interactions between age and family history/biopsies are omitted.
- Atypical hyperplasia is simplified to a single 1.82 multiplier; the clinical model fits a full interaction term.
- DCIS, lifestyle factors, mammographic density, and genetics (beyond first-degree relatives) are not included.
- Hazard is assumed constant within each 5-year age band.
Frequently asked questions
What is the Gail model?
The Gail model (published by Gail et al., Journal of the National Cancer Institute, 1989) estimates a woman's probability of developing invasive breast cancer from a small set of risk factors: age, age at first period, age at first live birth, number of first-degree relatives with breast cancer, number of breast biopsies, and atypical hyperplasia. The US National Cancer Institute later turned it into the clinical BCRAT (Breast Cancer Risk Assessment Tool).
Is this calculator the same as the NCI's clinical BCRAT?
No. This is a simplified educational adaptation of the Gail model, not the clinical BCRAT. It uses the published Gail relative risks and approximate SEER incidence rates, but it skips the clinical tool's reference-group baseline calibration, age interactions, and race-specific adjustments. Results are for learning only — use the official NCI tool (bcrisktool.cancer.gov) or talk to your doctor for clinical decisions.
What does the 5-year risk mean?
It is the estimated probability that a woman with your risk profile develops invasive breast cancer within the next 5 years. For example, 1.1% means roughly 11 out of 1,000 women with the same profile would be diagnosed in the next 5 years — and about 989 would not.
What does the lifetime risk mean?
It is the estimated probability of developing invasive breast cancer from your current age up to age 90, adjusted for the competing risk of dying from other causes first. Because it accounts for other-cause mortality, it is lower than simply adding up yearly risks.
Who should NOT use this tool?
Women with a personal history of breast cancer, DCIS, or LCIS, and women with a known BRCA1 or BRCA2 mutation — the Gail model was not designed or validated for them, and this tool will decline to give a number. It is also intended for women aged 35 to 85. If any of these apply to you, discuss risk assessment with your doctor or a genetic counselor.
Why might my result differ from the NCI BCRAT result?
The clinical BCRAT calibrates its baseline to the reference (lowest-risk) group using population attributable risk, includes interactions between age and some factors, and adjusts for race and ethnicity. This simplified version multiplies published relative risks onto population-average SEER rates, which can overestimate risk for low-risk profiles and misstate extreme combinations. Differences are expected — the clinical tool is the reference.
What is the 1.67% five-year risk threshold I keep reading about?
A 5-year risk of 1.67% or higher was used as an eligibility cutoff in the NSABP P-1 breast cancer prevention trial (Fisher et al., JNCI, 1998) studying tamoxifen. It is a research and clinical-discussion threshold, not a diagnosis. If your estimate is at or above it, that is a reason to talk with your doctor — not a reason to panic.
Does this tool assess hereditary (BRCA) risk?
No. The Gail model does not account for BRCA1/BRCA2 mutations or detailed family cancer patterns. If you have a strong family history of breast or ovarian cancer, especially at young ages, ask your doctor about genetic counseling and dedicated hereditary-risk models.
How is this different from the breast cancer recurrence tool (#519)?
Scope boundary: this tool (#520) estimates the chance of developing breast cancer for the first time (incidence) in women with no personal history of it. Tool #519 estimates the risk of cancer coming back (recurrence) for survivors who already had breast cancer. They answer different questions for different people and their numbers must not be compared.
Is my data sent anywhere?
No. This calculator runs 100% in your browser. Nothing you enter is transmitted, stored, or tracked — there is no server, no account, and no analytics on your inputs.
Free tool by NRTechStudio