Bone Density Calculator (T-Score/Z-Score)

Bone density scans produce raw numbers that only become meaningful once compared against standard reference populations — that's what the Bone Density Calculator (T-Score/Z-Score) does. Enter your gender, age, ethnicity, height, scan site, and BMD value from your DEXA report, along with the reference values for your age group, to get your T-Score, Z-Score, bone status (Normal, Osteopenia, or Osteoporosis), and relative fracture risk.

Gender *

years
cm
g/cm²

Bone Mineral Density from your DEXA scan report

g/cm²

Peak bone mass reference value for T-score calculation

g/cm²

Standard deviation for young adult reference population

g/cm²

Age-matched reference mean for Z-score calculation

g/cm²

Standard deviation for age-matched reference population

Results

T-Score

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Z-Score

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Bone Status

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Relative Fracture Risk

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Frequently Asked Questions

What is the difference between T-score and Z-score?

T-score compares your bone density to a healthy 30-year-old of the same gender at peak bone mass. Z-score compares your bone density to someone of your same age, gender, and ethnicity. T-score is used for diagnosing osteoporosis, while Z-score helps identify if bone loss is excessive for your age.

What T-score indicates osteoporosis?

A T-score of -2.5 or lower indicates osteoporosis. T-scores between -1.0 and -2.5 indicate osteopenia (low bone mass). T-scores of -1.0 or higher are considered normal bone density.

How accurate are bone density calculators?

These calculators provide standardized interpretations based on WHO criteria and are widely used in clinical practice. However, they should complement, not replace, professional medical evaluation. Your doctor will consider additional factors like medical history and risk factors.

What does a negative Z-score mean?

A Z-score below -2.0 is considered 'below the expected range for age' and may indicate secondary causes of bone loss that warrant further investigation. Z-scores above -2.0 are typically considered within the expected range for your age group.

Which scan site is most important for diagnosis?

The lumbar spine and hip (femoral neck or total hip) are the preferred sites for osteoporosis diagnosis. The forearm may be used when spine and hip cannot be measured or interpreted. The lowest T-score from any site is typically used for diagnosis.

How often should bone density be checked?

For postmenopausal women and men over 50, initial screening is recommended with follow-up every 1-2 years if osteopenia is present, or every 2-3 years if bone density is normal. Your doctor will determine the appropriate monitoring schedule based on your individual risk factors.

Can bone density scores improve with treatment?

Yes, with appropriate treatment including medications, calcium, vitamin D, and weight-bearing exercise, bone density can stabilize or improve. T-score improvements of 0.1 to 0.3 over 2-3 years are considered clinically significant responses to treatment.

What factors can affect bone density scan accuracy?

Factors that can affect DEXA scan accuracy include arthritis, previous fractures, metal implants, body size extremes, and recent barium studies. Movement during the scan and inconsistent positioning between scans can also impact results. Always inform your technologist of any relevant medical history.