FRAX Fracture Risk Calculator

FRAX Fracture Risk Calculator: Estimate Your 10-Year Hip and Major Fracture Probability

TL;DR: Enter your age, BMI, and clinical risk factors to get a 10-year probability of hip fracture and major osteoporotic fracture. A hip fracture risk of 3% or higher, or a major fracture risk of 20% or higher, triggers a recommendation for pharmacologic treatment under NOF/NOGG guidelines. The calculator above returns both percentages and a treatment recommendation in seconds.

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Table of Contents

• Your Bones Are Losing Density Right Now
• Six Scenarios Where This Calculator Changes Your Next Step
• FRAX Scoring Logic and the Variables Behind the Risk
• How to Enter Your FRAX Inputs Step by Step
• Putting the Formula to Work: Two Real-World Examples
• Where People Go Wrong With FRAX Results
• FAQ
• Assumptions and Notes
• Your Next Step
• Further Reading

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Your Bones Are Losing Density Right Now

After age 30, every adult loses roughly 0.5% to 1% of bone mineral density per year. For postmenopausal women, that rate can jump to 2% to 3% annually during the first five to seven years after menopause. The question is whether that loss puts you on a trajectory toward a fracture in the next decade.

The FRAX tool, developed by the WHO Collaborating Centre at the University of Sheffield (Kanis et al., 2008), answers that question with a specific number: your 10-year probability of a hip fracture and your 10-year probability of a major osteoporotic fracture (hip, spine, forearm, or humerus). It integrates clinical risk factors (gender, age, BMI, smoking status, glucocorticoid use, rheumatoid arthritis, prior fractures, parental hip fracture history, secondary osteoporosis, and alcohol intake) into a validated algorithm calibrated to country-specific fracture epidemiology.

A DXA scan measuring bone mineral density at the femoral neck can refine the estimate, but FRAX produces actionable results even without a DXA score. The algorithm works because fracture risk depends on more than bone density alone. Falls, cortical bone geometry, and microarchitectural deterioration all contribute, and the clinical risk factors serve as proxies for these variables.

Plug in your numbers above and get both probabilities before your next clinic visit.

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Six Scenarios Where This Calculator Changes Your Next Step

• You are a postmenopausal woman with osteopenia on a recent DEXA scan. A T-score between -1.0 and -2.5 places you in the osteopenia range, but that alone does not determine whether you need medication. Running your FRAX score adds clinical context: a 62-year-old woman with a femoral neck T-score of -1.8 and no other risk factors may land at 9% major fracture risk, well below the 20% treatment threshold. Add a parental hip fracture and glucocorticoid use, and that number can jump past 20%. The FRAX result tells you which side of the treatment line you fall on.

• Your doctor mentioned a DXA scan but you want to understand the result before the appointment. Roughly 54% of postmenopausal women have osteopenia, and many receive DXA results without context. Running a preliminary FRAX estimate using your clinical risk factors (without the DXA T-score) gives you a baseline probability to discuss. You will arrive at the appointment with a specific number and specific questions rather than a vague concern.

• You are a man over 70 and fracture risk has never been discussed. One in four hip fractures occurs in men, yet screening rates for male osteoporosis remain below 10% in primary care. A 72-year-old man with a BMI of 22, a history of smoking, and glucocorticoid use for COPD can easily exceed the 3% hip fracture threshold. Running the FRAX calculation identifies whether you should request a DXA referral or whether your risk is low enough to monitor with lifestyle measures alone.

• You take glucocorticoids (prednisone, prednisolone) for more than 3 months and want to quantify the bone impact. Glucocorticoid-induced osteoporosis is the most common form of secondary osteoporosis. Doses above 5 mg/day of prednisolone for 3 or more months increase fracture risk by 30% to 50% independent of bone density. FRAX includes a glucocorticoid checkbox, but the standard algorithm assumes a moderate dose. If your dose exceeds 7.5 mg/day, the true risk is higher than the FRAX output, and you should discuss dose-adjusted estimates with your clinician.

• You have rheumatoid arthritis and want to separate RA-related fracture risk from general aging. RA increases fracture risk through chronic inflammation, reduced mobility, and frequent glucocorticoid use. FRAX includes RA as an independent risk factor. A 58-year-old woman with RA, no prior fractures, and a BMI of 26 may score below treatment thresholds, but adding a prior wrist fracture and parental hip fracture can push the 10-year major fracture risk above 15%. Tracking your FRAX score annually quantifies whether your RA management is keeping bone risk stable or letting it drift upward.

• You are deciding whether calcium and vitamin D supplementation alone is sufficient or whether you need bisphosphonates. The NOF recommends pharmacologic treatment when the 10-year hip fracture probability reaches 3% or the major fracture probability reaches 20%. Below those thresholds, lifestyle interventions (calcium 1,200 mg/day, vitamin D 800 to 1,000 IU/day, weight-bearing exercise) are typically sufficient. The FRAX result draws a clear line between the two approaches.

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FRAX Scoring Logic and the Variables Behind the Risk

The FRAX algorithm is a set of Poisson regression models calibrated to country-specific fracture and mortality data. Each clinical risk factor carries an independent hazard ratio that modifies the baseline fracture probability for the patient's age and sex.

10-Year Fracture Probability =
  Baseline hazard (age, sex, country)
  × exp(sum of weighted clinical risk factors)
  × survival adjustment (competing mortality)

Clinical Risk Factor Weights (approximate hazard ratios from Kanis et al., 2008):
  Previous fracture:         HR ~1.85 for major fracture
  Parent hip fracture:       HR ~1.70 for hip fracture
  Current smoking:           HR ~1.30
  Glucocorticoids:           HR ~1.60
  Rheumatoid arthritis:      HR ~1.65
  Secondary osteoporosis:    HR ~1.20
  Alcohol ≥3 units/day:      HR ~1.70 for hip fracture
  BMI (continuous):          inverse relationship, lower BMI = higher risk
  Femoral neck T-score:      each 1 SD decrease ~1.5× hip fracture risk

FRAX Input Variables and Their Roles

NOF/NOGG Treatment Thresholds

Genetic variation plays a meaningful role in fracture susceptibility. Polymorphisms in the VDR (vitamin D receptor) and COL1A1 (collagen type I alpha 1) genes account for up to 5% to 10% of the variance in bone mineral density across populations. FRAX does not incorporate genetic markers directly, but parental hip fracture history serves as a partial proxy for heritable bone fragility.

The algorithm has known limitations. It does not account for dose-response relationships (it treats glucocorticoid use as binary), does not include fall risk or lumbar spine T-scores, and assumes all prior fractures carry equal weight regardless of site or recency. For patients with multiple vertebral fractures or very high glucocorticoid doses, FRAX may underestimate true risk by 10% to 20%.

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How to Enter Your FRAX Inputs Step by Step

1. Select your gender. FRAX uses sex-specific baseline hazard rates. Female baseline hip fracture incidence is approximately 2 to 3 times higher than male incidence after age 65 due to postmenopausal bone loss and longer life expectancy.

2. Enter your age. The calculator accepts ages 40 to 90. Below 40, the FRAX model is not validated because fracture incidence is too low to produce stable probability estimates. If you are between 40 and 50, your baseline risk is low unless multiple clinical risk factors are present.

3. Enter your BMI. Use your current weight and height. The default is 24 kg/m2. A BMI below 20 increases fracture risk because lower body weight means less mechanical loading on bone and less soft tissue cushioning during falls. A BMI above 30 is partially protective for hip fracture but increases ankle and proximal humerus fracture risk.

4. Check each clinical risk factor that applies. Previous fracture refers to any fragility fracture after age 40 (a fracture from a fall at standing height or less). Stress fractures and high-trauma fractures (car accidents, sports collisions) do not count. Parent hip fracture refers to biological mother or father only.

5. Mark smoking, glucocorticoids, rheumatoid arthritis, secondary osteoporosis, and alcohol intake honestly. Glucocorticoids means current or past exposure of ≥5 mg prednisolone equivalent daily for 3 or more months. Secondary osteoporosis includes conditions like type 1 diabetes, hyperthyroidism, premature menopause (before age 45), and chronic malabsorption.

6. Review outputs. The calculator returns three values: 10-year hip fracture probability (%), 10-year major osteoporotic fracture probability (%), and a treatment recommendation based on the NOF/NOGG thresholds.

7. Compare your result to the treatment thresholds. If your hip fracture risk is below 3% and your major fracture risk is below 20%, lifestyle interventions are the standard recommendation. If either threshold is met or exceeded, pharmacologic treatment (typically a bisphosphonate like alendronate) enters the conversation.

Non-obvious insight: FRAX calculates competing mortality risk, meaning it reduces fracture probability for patients with high mortality from other causes. A 78-year-old man with multiple comorbidities may show a lower FRAX score than expected because the algorithm accounts for the possibility he may die from cardiovascular disease before experiencing a fracture. This is clinically appropriate but can feel counterintuitive when discussing results.

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Putting the Formula to Work: Two Real-World Examples

Example 1: Postmenopausal Woman, Age 67, Osteopenia on DXA

Margaret is 67, female, with a BMI of 22.5 kg/m2. Her DXA scan shows a femoral neck T-score of -2.0 (osteopenia). She has no prior fractures, but her mother fractured a hip at age 74. She does not smoke, does not use glucocorticoids, does not have RA, no secondary osteoporosis, and drinks fewer than 3 units of alcohol per day.

Risk factors present: female, age 67, low-normal BMI (22.5), parental hip fracture (HR ~1.70 for hip), osteopenia T-score of -2.0.

Using the FRAX UK model with these inputs, the estimated probabilities are:

Margaret exceeds the 3% hip fracture threshold despite having only osteopenia, not osteoporosis. Her parental hip fracture history and age are the primary drivers. Her actionable step: discuss bisphosphonate therapy (alendronate 70 mg weekly is first-line) with her GP, alongside calcium and vitamin D supplementation. A follow-up DXA in 2 years will track whether treatment stabilizes or improves her bone density.

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Example 2: Male Retiree, Age 74, Glucocorticoid Use for COPD

Arthur is 74, male, BMI 21 kg/m2. He has taken prednisolone 7.5 mg daily for 14 months for COPD. He smokes. He fractured a wrist at age 68 after a fall. No parental hip fracture. No RA. No alcohol excess. Secondary osteoporosis is checked because of chronic glucocorticoid use.

Risk factors present: male, age 74, low BMI (21), previous fracture (HR ~1.85), current smoking (HR ~1.30), glucocorticoids (HR ~1.60), secondary osteoporosis (HR ~1.20).

Arthur exceeds both thresholds by a wide margin. His glucocorticoid dose (7.5 mg) actually exceeds the moderate-dose assumption built into FRAX, so his true risk is likely higher than 8.2% and 22%. His actionable step: urgent referral for DXA scanning if not already done, initiation of bisphosphonate therapy, vitamin D repletion (target serum 25(OH)D above 30 ng/mL), and a falls risk assessment given his age and steroid-related muscle weakness. His prescribing clinician should also review whether the prednisolone dose can be tapered or switched to an inhaled corticosteroid.

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Where People Go Wrong With FRAX Results

Ignoring the hip threshold and only checking major fracture risk. The NOF recommends treatment at either ≥3% hip fracture risk or ≥20% major fracture risk. Many patients focus only on the larger number (major fracture) and miss that their hip-specific risk already crossed the treatment line. In the example above, Margaret's major fracture risk was 16% (below 20%), but her hip risk of 4.8% already warranted treatment. Always check both numbers.

Counting high-trauma fractures as previous fractures. FRAX defines previous fracture as a fragility fracture, meaning one caused by a fall from standing height or less. A broken collarbone from a cycling crash at 30 km/h or a tibial fracture from a skiing accident does not count. Including high-trauma events inflates the previous fracture hazard ratio (1.85) when it should not apply, potentially pushing someone above a treatment threshold incorrectly.

Assuming FRAX replaces a DXA scan. FRAX works without DXA input, but adding a femoral neck T-score improves accuracy by approximately 10% to 15% for hip fracture prediction. Running FRAX without DXA is a screening step, not a final assessment. If your FRAX result is near a threshold (hip risk 2% to 4% or major risk 15% to 22%), a DXA scan is the next step to refine the estimate before making a treatment decision.

Using the wrong country model. FRAX is calibrated to country-specific fracture epidemiology. A patient in the UK running the US model (or vice versa) will get a different probability because background fracture rates differ. The UK has higher age-adjusted hip fracture incidence than several other European countries. Always confirm the calculator is set to your country of residence.

Entering BMI incorrectly by using pounds and inches without conversion. BMI requires weight in kilograms divided by height in metres squared. Entering weight as 165 (intending pounds) and height as 67 (intending inches) without converting produces a BMI of approximately 36.8 instead of the correct 25.8. That error shifts the fracture risk downward because higher BMI is partially protective in the FRAX model, potentially hiding a patient who should exceed a treatment threshold.

Running FRAX once and never repeating it. Fracture risk changes as you age and as clinical risk factors accumulate. A woman who scores 12% major fracture risk at age 60 may score 19% at age 67 purely from aging, and a new glucocorticoid prescription at age 65 could push her past 20% before the next scheduled DXA. Repeating the FRAX calculation every 2 to 3 years, or whenever a new risk factor appears, catches threshold crossings early enough to intervene.

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Assumptions and Notes

• Margin of error: FRAX probability estimates carry a confidence interval of approximately plus or minus 2 to 4 percentage points for hip fracture risk and plus or minus 5 to 8 percentage points for major fracture risk, depending on the number of risk factors present and the quality of the country-specific calibration data (Kanis et al., 2008). Results within 1 to 2 percentage points of a treatment threshold should be discussed with a clinician rather than used as a standalone treatment trigger.
• Professional disclaimer: This calculator implements the FRAX clinical risk factor algorithm for educational and screening purposes. It does not replace a clinical consultation. Treatment decisions should involve a DXA scan, clinical examination, and discussion with a qualified healthcare professional. The NOF/NOGG thresholds referenced apply to US and UK practice guidelines; other countries may use different intervention thresholds.

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Your Next Step

The two numbers that matter are your 10-year hip fracture probability and your 10-year major fracture probability. If either crosses the treatment line (3% hip, 20% major), that result is a conversation starter with your doctor, not a diagnosis. But it is a conversation worth having before the fracture happens.

Run the calculator above. Print or screenshot the result. Bring it to your next appointment.

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Further Reading

• Bone Density and DXA Score Explained: What Your T-Score Actually Means
• Calcium Intake Calculator: Find Your Daily Target for Bone Health
• BMI Category Checker: Understand How BMI Affects Fracture Risk