Detailed Breast Cancer Risk Calculator

How many of your sisters, daughters or mother had breast cancer?

Risk increases with number of first degree relatives affected.

How many benign breast biopsies have you had?

"Benign" means no cancer.  Have you ever had a biopsy result showing  "atypical hyperplasia"?

At what age did your menstrual cycles begin?

Risk increases with earlier menarche.

At what age did you give birth to your first child?

Risk increases with older age at first term live birth. (But if you have first degree relatives with carcinoma of the breast, then  risk goes down. Its a weird statistical thing).

What is your age?

Risk increases with age.  Age is the biggest risk factor. In other words,  all women have some risk. Hence the need to promote awareness and take steps for prevention.  76% of women who develop breast cancer had no other risk factors.

My Race is:

White women in North America have slightly higher risk than Black, Hispanic or Asian women, and considerably higher risk than women who have recently emigrated from Asia.


click for Gail Model and NSABP formula info.

Your chance of being diagnosed with breast cancer is estimated to be:  within lifetime (to age 90).

within 5 years,

within 20 years,

within 10 years,

within 30 years,

Your true risk could be somewhere within a range around these estimates.

The NCI's Breast Cancer Risk Assessment Tool website  has more decimal point accuracy (but only asks the first 6 questions, and is a bit of a pain to use).

Questions 7 to 12 below are additional risk modifiers.
The results will re-calculate automatically when you choose the pop-up menu items.

I am likely to undergo regular mammography screening.

Your chance of being diagnosed with carcinoma increases with regular (annual or biennial) mammographic screening, which is a good thing, because early diagnosis will probably save your life.

I am taking Tamoxifen.

Tamoxifen is a medicine that can reduce the risk of developing breast cancer in high risk women.  It's benefit to normal risk women is unknown.

My mammograms show dense breast tissue.  How dense?

Risk increases when breasts contain mammographically dense fibroglandular tissue.  Here's how you can find out your mammographic density.

Do you drink alcohol?

Risk increases with amount of alcohol consumed.  (One beer has 13 grams of alcohol, a glass of wine has 11 grams and a shot of liquor has 15 grams,  on average in the USA.)

Have you had a breast biopsy showing "lobular carcinoma in situ" (LCIS)?  If so, how old were you?

Risk increases if you had a previous breast biopsy showing LCIS (also called lobular neoplasia).

Have you used Birth Control Pills (BCPs)?

When did you start using BCPs?

When did you stop using BCPs?

Oral contraceptive Birth Control Pills can slightly increase your risk, but the extra cancers are mostly small and curable, and the slight risk gradually disappears when BCPs are no longer used.

Other risk factors exist, but they are regrettably not able to be included in this calculator. For example,    a personal history of breast ca or ovarian ca, therapeutic radiation treatment, having BRCA1 or BRCA2 gene mutations,  chemical exposures, obesity, smoking, etc.  If you have these or other risk factors, then this calculator's results will underestimate your risk.

The first part of the calculator uses the Gail model and is an emulation of the NCI's Breast Cancer Risk Assessment Tool, based on published risk statistics and methods gathered from peer-reviewed journals.

The second part of the calculator is the additional risk modifier questions, which are also based on published relative risk statistics. The methods used for combining extra relative risks are the standard approach, but the final calculated result cannot be compared to real data, which would require a 15-year study of a hundred thousand women, which is impossible. So remember, the results are estimates, and discussing your risk or breast symptoms with your own doctor, is always best.


Thank-you for visiting. I have two other important websites.

One site is breast cancer information. The other site is about my software project for the Talking Moose.

Please click to visit: the Talking Moose project website.


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November 28, 2015 by Dr. Halls