Wig cap sizes are not standardised across the industry, which is why a medium from one seller fits and a medium from another does not. What is consistent is the measurement behind the label. Work from inches and centimetres rather than the word on the listing and you will get it right first time.
The chart
The number that decides your size is head circumference: tape around the head just above the ears, across the hairline at the front, and round the occipital bone at the back.
| Size | Circumference (in) | Circumference (cm) | Roughly who |
|---|---|---|---|
| Petite | 20–20.5" | 51–52 cm | Small adult frames, teens |
| Petite / Average | 21–21.5" | 53–54.5 cm | The lower half of adults |
| Average (medium) | 21.5–22.5" | 54.5–57 cm | Around 80% of adults |
| Average / Large | 22.5–23" | 57–58.5 cm | Taller or broader frames |
| Large | 23–24" | 58.5–61 cm | Dense natural hair, larger heads |
If a listing gives you only S / M / L with no inches, ask before you buy. A seller who cannot tell you the circumference of their own cap is guessing, and so are you.
The other measurements that matter
Circumference decides the size. Two more decide whether that size will actually sit right:
| Size | Front to nape | Ear to ear over the top |
|---|---|---|
| Petite | 13–13.5" | 11–11.5" |
| Average | 14–14.5" | 12–12.5" |
| Large | 15–15.5" | 13–13.5" |
A head can be average in circumference and large front to nape, which is the usual reason a correctly sized cap still sits too far forward and pushes the lace behind the real hairline. The measuring guide walks through taking all five numbers properly.
How much adjustment a cap gives you
Nearly every unit has two adjustable straps at the nape. Between them they give about an inch of range — roughly half an inch in each direction from the cap’s nominal size. That is why a medium genuinely covers 21.5 to 22.5 inches.
It also means adjustment cannot rescue a cap that is a full size out. Straps pull the back in; they do nothing for the distance from your forehead to your crown, and nothing for a cap whose lace is wider than your hairline.
If you are between sizes, go down
A slightly small cap tightens into a secure fit. A slightly large cap never stops moving, and movement is what makes an install look obvious, lifts the lace at the temples, and rubs the nape hair against your collar until it mats — the mechanism described in the tangling guide.
The exception is front to nape, as above. If that number is long for the size, go up and tighten the straps instead.
Cap construction changes how size feels
- Standard wefted cap — stretchy bands between wefts, so it has the most give. Forgiving of a half-inch either way.
- Full lace — the least stretch. Size matters most here.
- Glueless / wear and go — an elastic band plus combs doing all the holding, so fit is the entire security system. See what a glueless wig actually is.
- U-part — sits over your own hair at the parting, which effectively adds a little bulk. Some people size up a touch.
Maya is our U-part unit, and Nia is a glueless bob where the cap is doing the work — both are worth measuring for rather than estimating. The full glueless collection is built around adjustable caps.
Signs the size is wrong
Too big: the unit creeps backward through the day, the lace lifts at the temples, you need more adhesive than the instructions suggest, or there is a visible gap at the nape when you look down.
Too small: a band of pressure across the forehead or behind the ears, a headache by mid-afternoon, the nape riding up to expose your own hair, or a seam you can feel the whole time you are wearing it.
Neither is something to put up with. If the unit has not been worn or altered, our returns policy covers an exchange for the right size.
Children and petite adults
Heads below 20 inches are outside standard adult sizing. A petite cap taken in at the straps will usually work down to about 19.5 inches, but below that the front-to-nape distance becomes the limiting factor rather than the circumference, and the lace will sit wrong no matter how tight you pull the back.
What to do next
Measure first, then choose construction and density — our size and density guide covers what we stock, and which wig should I buy runs through the whole decision in order. If your numbers sit awkwardly between two sizes, send them to us on the contact page and we will tell you which cap to take.