Inputs
All inputs use this unit.
cm
Tape at the base of the neck, level and snug.
cm
cm
cm
cm
Uses Ramanujan's approximation:
π·(3(a+b) − √((3a+b)(a+3b))), where a=w/2, b=d/2.
in
Typical shirt collar sizes are in inches.
in
Results
| Quantity | Value | Unit | Notes |
|---|
Tip: Results include both centimeters and inches for clarity.
Formula used
For direct tape or collar inputs, circumference is the entered value (plus optional allowance). For elliptical estimation from width and depth, this calculator applies Ramanujan’s first approximation:
C ≈ π·(3(a+b) − √((3a+b)(a+3b))), where a = width/2 and b = depth/2.
Equivalent circle diameter is D = C/π, and cross‑sectional area is A = C²/(4π).
How to use this calculator
- Select your preferred method: direct tape, width+depth, or dress collar.
- Choose units. Inputs and allowances will follow this selection.
- Enter required values. Optionally enable and set a fit allowance.
- Press Calculate. Results will show circumference, diameter, and area.
- Use Download CSV or Download PDF to save records.
Example data
| # | Method | Inputs | Allowance | Circumference (cm) | Circumference (in) |
|---|---|---|---|---|---|
| 1 | Direct tape | C = 37.5 cm | 0.5 cm | 38.00 | 14.96 |
| 2 | Width+Depth | W = 14.0 cm, D = 12.0 cm | 0.5 cm | 40.13 | 15.80 |
| 3 | Dress collar | Collar = 15.5 in | 0.5 in | 40.64 | 16.00 |
Values are illustrative and rounded; real measurements vary by anatomy and technique.
FAQs
Place the tape at the base of the neck, level to the floor, snug but not tight, and avoid compressing skin or soft tissue excessively.
Common allowances range from 0.5–1.5 cm (≈0.2–0.6 in) depending on comfort, fabric, and style. Formal collars often include a small built‑in allowance.
Necks are not perfect circles. Using width and depth approximates an ellipse, giving a more tailored estimate when a full tape measurement is inconvenient.
It provides precise circumference values and conversions. If using within medical formulas, follow the specific protocol for measurement sites and posture.
Yes. Many collars use quarter‑inch increments. Use the displayed inch value and round to the nearest 0.25 in as preferred.