Osteoporosis Risk Calculator

Osteoporosis is a disease where bones lose density and become weak enough to break easily. It is often called a silent disease, because most people have no symptoms until a bone breaks⁵. This calculator uses a simple screening score based on age and body weight to estimate how likely low bone density is.

What the OST Score Measures

The Osteoporosis Self-assessment Tool (OST) estimates the chance that a bone density scan would show osteoporosis. It does not measure your bones. Older age and lower body weight both raise the chance of low bone density, so the score combines just those two numbers. A lower score means a higher risk.

The Formula

OST score = (weight in kg minus age in years) x 0.2

Drop the decimals to get a whole number.

The score was first built and tested in postmenopausal women across eight Asian countries¹.

How This Calculator Computes Your Result

Enter your sex, age and weight in kilograms or pounds. Pounds are converted to kilograms (1 lb = 0.45359237 kg), the formula is applied, and the decimals are dropped to give a whole number. Women are asked whether they have Asian ancestry, because this decides which study's cut-offs apply. Women aged 45 and over can also answer one question about current estrogen or hormone therapy to see a second score, the ORAI.

What Your Result Means

Each set of cut-offs comes from a different group of people. The calculator shows the set that matches you.

In the original Asian study, 61% of women in the high band had osteoporosis, compared with 15% in the medium band and 3% in the low band¹. About 40% of women fell into the low band¹. The US Preventive Services Task Force (USPSTF) lists an OST score under 2 as a frequently used threshold for increased risk². The men's bands come from a study of 128 African American male veterans, where OST predicted low bone mass with an AUC of 0.83 (1.0 is perfect, 0.5 is chance)³.

The Optional ORAI Score for Women

The Osteoporosis Risk Assessment Instrument (ORAI) was built in Canadian women aged 45 and over⁴. It adds points for age, weight and not taking estrogen.

A total of 9 or more met the developers' cut-off for a bone density test. At that cut-off, ORAI found 93% of women with low bone density but also flagged many women without it⁴. OST and ORAI can disagree. For example, a 58-year-old woman weighing 154 lb who does not take estrogen gets an OST of 2 (not flagged) but an ORAI of 10 (meets the cut-off).

Who Is Screened for Osteoporosis

The USPSTF updated its recommendation in January 2025². It recommends screening for women 65 and older. It also recommends screening for postmenopausal women younger than 65 who are at increased risk, as found by a clinical risk tool such as OST or ORAI². For men, the USPSTF found the evidence insufficient to judge the benefits and harms of screening, which is not a recommendation against it². Osteoporosis is much more common in women: 19.6% of US women aged 50 and over have it, compared with 4.4% of men².

Risk Factors the Score Does Not Include

OST and ORAI use only a few inputs. Other known risk factors include a parent with osteoporosis or a hip fracture, low calcium and vitamin D intake, low physical activity, smoking, heavy drinking, some medical conditions and long-term use of certain medicines⁵. The USPSTF also names a parent's hip fracture, smoking and excess alcohol as risk factors, and long-term use of medicines such as glucocorticoid steroids as a cause of bone loss². If you have several of these, a low-risk OST result tells you less.

OST Versus FRAX

FRAX is a separate, licensed tool that estimates your 10-year chance of a hip fracture and of a major osteoporotic fracture (spine, forearm, hip or shoulder)⁶. It uses many more risk factors and can include a bone density result. This calculator does not reproduce FRAX. You can use it on the [official FRAX site](https://www.fraxplus.org/)⁶.