FRAX Fracture Risk Calculator

How to Use This Calculator

1. Enter age, sex, weight, height, and clinical risk factors.
2. 10-year major osteoporotic and hip fracture probabilities display instantly.
3. With BMD tab: add femoral neck T-score for more accurate estimates.
4. Professional tier adds NOF treatment decision and pharmacology recommendations.

Formula

Example

Frequently Asked Questions

• What is the FRAX score? ▼
  FRAX (Fracture Risk Assessment Tool) is a web-based algorithm developed by Professor John Kanis at the University of Sheffield (UK) and published in Osteoporosis International in 2008. It calculates the 10-year probability of major osteoporotic fracture (clinical vertebral, hip, distal forearm, and proximal humerus fractures) and the 10-year probability of hip fracture specifically, expressed as percentages. FRAX integrates 11 clinical risk factors: age, sex, body weight, height (used to calculate BMI), prior fragility fracture, parental history of hip fracture, current cigarette smoking, long-term glucocorticoid use (≥5 mg prednisolone/day for ≥3 months), rheumatoid arthritis, secondary osteoporosis causes (hypogonadism, inflammatory bowel disease, prolonged immobilization, type 1 diabetes, chronic liver disease), and alcohol consumption ≥3 units/day. Optionally, the femoral neck bone mineral density (BMD) T-score from DXA can be incorporated to improve accuracy. FRAX is country-specific — the algorithm is calibrated to national fracture and mortality epidemiology for over 65 countries. The US version is calibrated to NHANES/US population data. This means the same risk factors in different countries yield slightly different absolute probabilities, reflecting true differences in baseline fracture incidence. The tool is endorsed by the National Osteoporosis Foundation (NOF), AACE, ESCEO, and the International Osteoporosis Foundation (IOF).
• Should I include BMD in my FRAX calculation? ▼
  Including femoral neck BMD T-score from DXA significantly improves FRAX accuracy and should be used whenever available. Without BMD, FRAX uses only clinical risk factors, which capture population-level risk but miss individual bone density variation. Two patients with identical clinical risk factors but T-scores of −1.0 and −3.0 have very different actual fracture risks; FRAX without BMD cannot distinguish between them. The key guidance on when to use FRAX with BMD: the tool is most helpful for patients in the intermediate risk range based on clinical factors alone (FRAX major fracture risk 10–20%), where BMD results can shift the decision toward or away from pharmacological treatment. For patients with very high clinical risk (multiple major risk factors, prior fragility fracture) or very low risk, adding BMD is less likely to change the management decision. NICE UK guidelines (TA161) and NOF recommend using BMD-adjusted FRAX when available. Importantly, FRAX uses only the femoral neck T-score — not spine T-score — because hip DXA has better standardization across centers and better fracture predictive validity. If spine BMD is disproportionately low (due to vertebral deformity or severe OA at the spine), hip BMD may be the more reliable measure. Trabecular Bone Score (TBS) is an additional texture parameter from DXA images that can be incorporated into FRAX via a simple adjustment to further improve discrimination, particularly useful when spine or hip BMD alone may be misleading.
• What FRAX score warrants treatment? ▼
  In the United States, the National Osteoporosis Foundation (NOF) 2023 Clinician's Guide recommends pharmacological treatment when FRAX 10-year hip fracture probability is ≥3% or FRAX 10-year major osteoporotic fracture probability is ≥20%. These thresholds were established based on cost-effectiveness analyses (Dawson-Hughes et al.) showing that treatment at these levels is economically justified at US healthcare costs. In the UK, NICE uses an intervention threshold based on age-specific FRAX risk (the "assessment threshold" or "intervention threshold" varies by age and increases with age). In most other European countries, the intervention threshold is set at the country-specific level equivalent to the fracture risk of a woman aged 65 with no other risk factors. Automatic treatment indications regardless of FRAX score: a T-score ≤−2.5 at spine or hip (densitometric osteoporosis) with or without fragility fractures; a prior hip fracture or vertebral fracture — these alone warrant treatment. FRAX is specifically designed for the "gray zone" of osteopenia (T-score −1.0 to −2.5) where the treatment decision is less obvious without fracture risk quantification. First-line pharmacological options: bisphosphonates (alendronate, risedronate) for most patients; intravenous zoledronic acid if oral bisphosphonate intolerance; denosumab as alternative; romosozumab or teriparatide for very high risk (T-score ≤−3.0, multiple fractures, or failed bisphosphonate therapy).
• Why does FRAX have country-specific versions? ▼
  FRAX requires country-specific calibration because the absolute incidence of hip and other osteoporotic fractures, and the age-specific mortality rates that compete with fracture risk, vary enormously between countries. The fundamental epidemiology differs: Scandinavian countries (Sweden, Norway, Denmark) have among the world's highest hip fracture rates; Southern European (Spain, Italy), African, and Asian countries have substantially lower rates. Using a single universal model would systematically over- or underestimate fracture risk in different populations. The calibration process uses national epidemiological data on: hip fracture incidence rates by age and sex from population-based registries or survey studies; all-cause mortality rates by age and sex from national vital statistics. The FRAX equations then calculate absolute probability by combining the hazard of fracture with the competing hazard of death. Country-specific calibration also incorporates the relative contribution of clinical risk factors (e.g., the relative risk of smoking or glucocorticoids on fracture may differ between populations due to different baseline smoking rates or different patterns of corticosteroid prescribing). There are currently FRAX models for over 65 countries and regions, with some countries having ethnicity-specific models (the US has separate models for White, Black, Hispanic, and Asian Americans). When a specific country model is unavailable, clinicians are advised to use the model from the nearest calibrated country. Online FRAX calculation at shef.ac.uk/FRAX remains the most accurate method because it uses the full non-linear regression equations.
• How often should FRAX be reassessed? ▼
  FRAX reassessment frequency depends on the individual's baseline risk category and whether treatment has been initiated. General recommendations from the International Osteoporosis Foundation, NOF, and ESCEO: Low-risk patients (FRAX major fracture <10%, no BMD, no prior fracture): FRAX reassessment can be deferred for 5 years. BMD measurement is often unnecessary in this group unless risk factors change significantly. Moderate-risk patients (FRAX major fracture 10–19%): reassess FRAX with BMD in 2–3 years, or sooner if new risk factors develop (new fracture, glucocorticoid initiation, significant weight loss). High-risk patients on treatment: do not routinely reassess FRAX during treatment because FRAX is not validated to track treatment response — use DXA BMD change for monitoring therapeutic efficacy. After 3–5 years of bisphosphonate treatment, a "drug holiday" assessment is performed using updated FRAX and BMD. Post-drug holiday: reassess FRAX annually or when BMD has declined significantly (>5% loss). Patients with new fragility fracture: FRAX should be recalculated because a new fracture substantially increases subsequent fracture risk (the "imminent fracture risk" in the 1–2 years following an incident fracture is 2–10× the FRAX estimate — FRAX underestimates this short-term elevated risk, which is why many guidelines recommend treatment after any fragility fracture without waiting for FRAX calculation). Important caveat: FRAX assumes no current treatment with bone-active agents — it should not be used to predict fracture risk in patients currently on bisphosphonates, denosumab, or other anti-osteoporotic medications.

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