Estimate your osteoporosis screening risk band from body weight and age using the OST (Osteoporosis Self-Assessment Tool) index — a simple formula most validated in postmenopausal women.
Osteoporosis is a condition where bones become weak, thin and porous, making them more likely to fracture — often with no symptoms until a break actually happens. This calculator does not diagnose osteoporosis. It applies the OST index, a simple, validated screening formula using only your body weight and age, to flag whether you fall into a Low, Moderate or High risk band for low bone density, and whether a bone density (DXA) scan may be worth discussing with your doctor.
⚕️ Medical Notice: This calculator uses only body weight and age — the two inputs of the validated OST index. It does not account for other major osteoporosis risk factors a doctor would also consider, such as previous fractures, family history of hip fracture, smoking, excess alcohol, long-term corticosteroid (glucocorticoid) use, rheumatoid arthritis, early menopause, low calcium or vitamin D intake, or low physical activity. A low-risk score does not rule out osteoporosis, and a moderate or high score does not confirm it — only a DXA (dual-energy X-ray absorptiometry) bone density scan, ordered by a doctor, can diagnose osteoporosis.
| Parameter | Value |
|---|
The OST index is deliberately simple — it uses only your body weight and age, with no blood tests, scans or questionnaires required as inputs to the formula itself.
| Risk Category | OST Index Range | What It Suggests |
|---|---|---|
| Low Risk | Above −1 | Screening suggests a lower likelihood of low bone density |
| Moderate (Intermediate) Risk | −1 to −4 (inclusive) | Worth discussing whether a DXA bone density scan is appropriate |
| High Risk | Below −4 | A DXA bone density scan is generally recommended |
The OST index deliberately keeps things simple by using only weight and age. A full clinical risk assessment — the kind your doctor may carry out — also weighs up a range of other factors, including:
If any of these apply to you, it may be worth discussing bone health with your doctor even if your OST index suggests low risk.
Osteoporosis is a condition in which bones lose density and become weak, thin and porous, making them more likely to break — often from a fall or bump that would not normally cause a fracture. It typically develops silently over many years, usually with no symptoms until a fracture occurs, which is why it is sometimes described as a silent condition. Bone density naturally declines with age, and the drop in oestrogen after menopause accelerates bone loss in women, which is why postmenopausal women are the group most commonly targeted for osteoporosis screening.
| OST Index | Risk Category | General Guidance |
|---|---|---|
| Above −1 | Low Risk | Continue routine bone-healthy habits; no immediate action indicated by this screen alone |
| −1 to −4 (inclusive) | Moderate (Intermediate) Risk | Consider discussing a DXA bone density scan with your doctor, especially if other risk factors are present |
| Below −4 | High Risk | A DXA bone density scan is generally recommended to check for osteoporosis |
The OST index was originally developed and validated in studies of postmenopausal women, and this remains the population in which it performs most reliably as a screening step. Because bone loss accelerates sharply after menopause due to falling oestrogen levels, postmenopausal women are also the group most commonly targeted for osteoporosis screening in clinical guidance. The formula has also been studied in men and in other groups, and can still be a useful quick check for them, but its predictive performance is generally considered less well established outside the postmenopausal population it was originally built and tested in.
What is the OST index and how is it calculated?
The OST (Osteoporosis Self-Assessment Tool) index is a simple, validated screening formula that estimates osteoporosis risk using only body weight and age. It is calculated as (Weight in kg - Age in years) × 0.2. The result places you into a Low, Moderate (Intermediate) or High risk band for low bone density.
Who is the OST index most useful for?
The OST index was originally developed and validated in studies of postmenopausal women, and it performs best in this group. It has also been studied in men and other populations, though its accuracy can differ outside the postmenopausal group it was built for. It is best used as a quick screening step, not a substitute for a full clinical assessment.
What does a Low Risk result mean?
A Low Risk result (OST index above -1) suggests a lower likelihood of low bone density based on this screening formula alone. It does not rule out osteoporosis entirely, since the OST index only considers weight and age and ignores other risk factors such as smoking, family history or medication use.
What does a Moderate or High Risk result mean?
A Moderate (Intermediate) Risk result (OST index between -1 and -4) or a High Risk result (OST index below -4) suggests it may be worth discussing a DXA bone density scan with your doctor. Neither result confirms osteoporosis on its own — only a DXA scan, interpreted by a doctor, can do that.
Can this calculator diagnose osteoporosis?
No. This calculator is a screening tool only. Osteoporosis can only be diagnosed by a dual-energy X-ray absorptiometry (DXA) bone density scan, ordered and interpreted by a qualified doctor. This tool simply estimates whether that conversation may be worthwhile based on your weight and age.
What risk factors does the OST index not account for?
The OST index only uses weight and age. It does not account for previous fractures, family history of hip fracture, smoking, excess alcohol intake, long-term corticosteroid (glucocorticoid) use, rheumatoid arthritis, early menopause, low calcium or vitamin D intake, or low physical activity — all of which a doctor would also consider when assessing your bone health.
Is the OST index accurate for men?
The OST index was developed and validated primarily in postmenopausal women. Research has also examined its use in men, generally finding it can still flag men who may benefit from further testing, though its performance is not as extensively validated in men as it is in postmenopausal women. Men with risk factors for osteoporosis should still discuss bone health with their doctor regardless of their OST result.
What is a DXA bone density scan?
A DXA (dual-energy X-ray absorptiometry) scan is a low-radiation imaging test, usually of the hip and spine, that measures bone mineral density. It is the standard clinical test used to diagnose osteoporosis and osteopenia, and it is the test your doctor may recommend if your OST screening result suggests moderate or high risk.
Can I enter my weight in pounds instead of kilograms?
Yes. Use the weight units toggle to switch between kilograms and pounds. The calculator converts your entry to kilograms internally before applying the OST index formula, so your risk category will be the same regardless of which unit you enter.
How often should postmenopausal women be screened for osteoporosis?
There is no single answer that applies to everyone — this depends on individual risk factors, age and prior results, and should be decided with your doctor. Many postmenopausal women use tools like the OST index as a quick first check, with a DXA scan considered if the result, symptoms or other risk factors suggest it may be useful.