Surface Based Body Shape Index Calculator

Calculator Form

Unit system

Sex for reference view

This changes the contextual reference sample only.

Age (optional)

Decimal precision

Height (cm)

Weight (kg)

Waist circumference (cm)

Vertical trunk circumference (cm)

Measure from the shoulder, through the crotch, and back to the shoulder.

Clear Form

Example Data Table

Profile	Height (cm)	Weight (kg)	Waist (cm)	VTC (cm)	BSA (m²)	SBSI	Reference Percentile
A	165	60	74	168	1.6364	0.0998	11.9%
B	172	72	86	176	1.8223	0.1043	32.1%
C	178	85	98	184	2.0052	0.1073	50.8%
D	160	90	110	172	1.9177	0.1097	65.4%

These examples are for understanding the calculator layout and output style. They are not treatment targets.

Formula Used

SBSI Core Formula SBSI = (H^7/4 × WC^5/6) / (BSA × VTC)

Body Surface Area BSA (m²) = 0.00949 × Weight^0.441 × Height(cm)^0.655

Body Mass Index BMI = Weight(kg) / Height(m)²

Waist to Height Ratio WHtR = Waist(cm) / Height(cm)

ABSI ABSI = Waist(m) / (BMI^2/3 × Height(m)^1/2)

Meaning of inputs: Height is standing height. Waist circumference is the horizontal waist measure. Vertical trunk circumference is the shoulder-through-crotch loop measure. Body surface area adds overall body size into the index.

Interpretation note: This page converts SBSI into a reference percentile using published sample averages and variation. That provides context, not a universal clinical verdict.

How to Use This Calculator

Choose metric or imperial units.
Enter height, weight, waist circumference, and vertical trunk circumference.
Select a reference view if you want overall, female, or male contextual comparison.
Choose decimal precision for the displayed output.
Press Calculate SBSI to show results above the form.
Review the main index, BMI, BSA, WHtR, ABSI, percentile, and interpretation band.
Use the Plotly graph to see how changing waist size would shift SBSI.
Download the current results as CSV or PDF when needed.

Frequently Asked Questions

1. What does SBSI measure?

SBSI combines height, waist circumference, vertical trunk circumference, and body surface area into one body-shape indicator. It tries to reflect both size and shape instead of weight alone.

2. Why is vertical trunk circumference required?

VTC adds a vertical torso dimension that waist circumference alone cannot capture. That makes SBSI more shape-aware and helps distinguish people with similar weight or BMI but different body distributions.

3. Is SBSI better than BMI?

SBSI is more detailed than BMI because it uses several body measurements. BMI is still useful for quick screening, but SBSI can provide richer context about body shape.

4. Does this calculator diagnose health conditions?

No. This tool is educational and informational. It can help organize body-measurement context, but diagnosis and treatment decisions should come from a qualified healthcare professional.

5. What is the percentile in the result section?

It places your SBSI against a reference distribution used for context. A higher percentile means your value is higher relative to that reference sample, not that disease is certain.

6. Can I use imperial units?

Yes. The form accepts feet, inches, pounds, and inch-based circumferences. The script converts everything internally to metric units before running the formulas.

7. Why does the graph vary only waist circumference?

The graph isolates one major shape variable so you can see directional sensitivity clearly. Height, weight, and VTC stay fixed to make the change easy to understand.

8. When should I export CSV or PDF?

Use CSV for spreadsheet work, research notes, or batch comparisons. Use PDF when you want a clean summary for sharing, saving, or printing.