Select finished collar circumference, neck circumference or total ease allowance, then enter the two required measurements. Inputs and results support inches, cm, ft and m.
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Collar Size Formula
Here, collar size means the finished collar circumference: neck circumference plus a chosen total ease allowance. Ease is extra room around the whole neck, separate from seam allowance. This arithmetic does not determine a brand label size or guarantee fit.
- CS = collar size
- NC = neck circumference
- EA = ease allowance
The calculator can solve for any missing value when you enter the other two:
- Calculate collar size: adds your neck circumference and ease allowance.
- Calculate neck circumference: subtracts the ease allowance from the collar size.
- Calculate ease allowance: subtracts the neck circumference from the collar size.
All values are converted to centimeters internally, then converted to the selected result unit using exact length conversions.
Illustrative Collar Ease Calculations
These examples show the arithmetic for chosen allowances, not universal fit recommendations. Confirm the allowance with your garment or pattern supplier.
| Neck circumference | Chosen total ease | Finished collar circumference |
|---|---|---|
| 15.5 in | 0.75 in | 16.25 in |
| 40 cm | 2 cm | 42 cm |
| 16 in | 0 in | 16 in |
Common Collar Size Unit Conversions
| Measurement | Equivalent |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 12 inches |
| 1 meter | 39.3701 inches |
| 40 cm | 15.748 inches |
Example Collar Size Calculations
Example 1: Calculate collar size
You measure a neck circumference of 15.5 in and want 0.75 in of ease.
The collar size is 16.25 in.
Example 2: Calculate ease allowance
You have a collar size of 42 cm and a neck circumference of 40 cm.
The ease allowance is 2 cm.
FAQ
How do you measure neck circumference for collar size?
Wrap a flexible measuring tape around the base of the neck where the collar normally sits. Keep the tape level and close to the skin, but do not pull it tight. That measurement is the neck circumference. Add your chosen ease allowance to get the collar size.
What ease allowance should you use for a shirt collar?
Use the garment or pattern supplier’s measurement method and ease allowance. Fabric, style and fit preference matter. If your measurement or the brand’s size already includes ease, do not add it again. The examples above are arithmetic illustrations, not recommended fit ranges.
Why does the calculator reject some values?
Collar and neck circumferences must be positive; ease may be zero. The collar must exceed the ease allowance for a positive neck result and must be at least as large as the neck for a nonnegative ease result.
