Wig Size Guide UK: How to Measure Your Head for a Wig

TL;DR — Most women fit an Average wig cap (21.5"–22.5" / 54–57 cm). To find your size, take a soft tape measure and run it from the centre of your forehead, around above one ear, down to the nape of your neck, then back up around the other ear to where you started. That single circumference measurement tells you 90% of what you need to know — Petite (20.5–21.5" / 52–54 cm), Average (21.5–22.5" / 54–57 cm) or Large (22.5–23.5" / 57–60 cm). All Ailsa's wigs include adjustable straps inside the cap to fine-tune the fit.

Wig Cap Size Chart (UK)

Use the chart below to match your head circumference to a UK wig cap size. The vast majority of adult women fall into the Average bracket, which is why every Ailsa's wig is built to an Average cap by default unless the listing says otherwise. Petite and Large options are also available for smaller and larger head frames.

Cap Size	Head Circumference (inches)	Head Circumference (cm)	Best For
Petite	20.5" – 21.5"	52 – 54 cm	Smaller head frames, finer bone structure
Average	21.5" – 22.5"	54 – 57 cm	Most adult women (around 80% of customers)
Large	22.5" – 23.5"	57 – 60 cm	Fuller head shapes, thicker bio-hair underneath

How to Measure Your Head for a Wig — 4 Steps

You only need one tool: a soft cloth tape measure (the kind dressmakers and tailors use). If you don't have one, a piece of string and a ruler will do — wrap the string around your head, mark where it overlaps, then measure the length against a ruler. Take all four measurements with your hair flat against your scalp, in the same way you'll wear it under the wig.

Step 1: Circumference (Forehead → Ear → Nape → Ear → Forehead)

This is the most important measurement and the one the size chart above is based on. Place the start of the tape at the centre of your forehead, just above the natural hairline. Take the tape around above one ear, down to the bony bump at the nape of your neck (the occipital bone), then around above the other ear and back to where you started. The tape should be snug but not tight — you should be able to slide a finger comfortably underneath it. Make a note of the number in inches and centimetres.

Step 2: Front to Nape

Place the tape measure at the very centre of your hairline at the front, then run it straight back over the top of your head, following the natural curve, all the way to the nape of your neck. This measurement tells you whether a wig will sit too far forward (covering your eyebrows) or too far back (showing your natural hairline). The UK average is around 13.5"–14.5" / 34–37 cm.

Step 3: Ear to Ear (Over the Top)

Place the tape at the top of one ear where it meets your scalp. Run the tape over the crown of your head and down to the same point above the other ear. This measurement matters most for shorter wigs and bobs, where any sizing error is much more visible. The UK average is around 12"–13" / 30.5–33 cm.

Step 4: Temple to Temple (Round the Back)

This one is the opposite of Step 3. Place the tape at one temple (the soft area beside your eye), then run it around the back of your head at ear level until it reaches the other temple. This measurement helps you confirm cap depth — useful if you have a high or low forehead. The UK average is around 14"–15" / 35.5–38 cm.

Quick reference — typical UK averages:

• Circumference: 22" / 56 cm
• Front to nape: 14" / 35.5 cm
• Ear to ear over top: 12.5" / 31.5 cm
• Temple to temple round back: 14.5" / 37 cm

Choosing the Right Cap Construction

Cap construction affects fit, comfort and how the wig looks at the hairline. Here's what to look for in your size range.

Lace Front

A sheer lace panel runs along the forehead, creating an undetectable hairline that you can pull back from your face. Lace front caps typically run true to size — pick the size that matches your circumference. Browse our lace front wig collection for a natural-looking front edge.

Monofilament (Mono Top)

A breathable mesh top makes the parting and crown look like real scalp. Mono top caps tend to run slightly more generous because the mesh has more give than wefted material. If you're between sizes, a monofilament wig often fits comfortably even at the smaller end of the range.

Glueless

Glueless wigs are designed to stay put without tape, glue or wig grip — perfect if your circumference falls right inside the size range without needing to cinch the straps too tight. Our glueless wigs collection uses ear tabs, silicone strips and adjustable bands to lock the cap in place.

Open-Wefted (Capless)

Wefts of hair are sewn onto thin elastic strips with open spaces in between, so air flows freely against the scalp. Open-wefted caps are extremely stretchy — they can comfortably accommodate someone who measures right between Average and Large.

Adjustable Features Inside a Wig

Every modern wig is built with at least one of the following adjustment features. Knowing what's inside your cap means you can fine-tune the fit yourself in seconds.

• Adjustable straps with hooks — Two velcro or hook-and-eye tabs sit at the nape of the neck. Tightening them takes in roughly half an inch on each side, for a total of about 1 inch (≈2.5 cm) of adjustment. This is the most common adjuster on Ailsa's wigs.
• Combs — Small plastic combs are sewn into the front, sides and back of the cap. You slot them into your bio-hair to anchor the wig in place. They don't change the cap size, but they stop a slightly loose wig from sliding.
• Silicone strips — Thin silicone strips are stitched along the inside band, adding grip against the scalp. This is especially useful if you have alopecia, are post-chemotherapy, or simply have very smooth skin.
• Elasticated band — A thin elastic band runs around the perimeter of the cap, stretching to give around half an inch of extra room. Most caps have one of these built into the standard construction.
• Ear tabs — Small reinforced flaps that sit just in front of the ears. They keep the wig anchored and stop it from rotating during the day.

Wig Size vs Cap Size vs Hair Length

One thing that confuses first-time wig buyers: cap size has nothing to do with hair length. A 12" bob and a 24" long wig in the same brand will both come in Petite, Average and Large cap sizes. The cap is the foundation that sits against your scalp; the hair is what's sewn onto it. So when you see a measurement like "16 inches" on a product page, that's the length of the hair, not the size of the cap.

Equally, "wig size" and "wig cap size" mean the same thing in the UK industry — both refer to how the cap fits your head. Different brands sometimes use slightly different language (Petite/Small/Mini, or Average/Medium/Standard) but the inch and cm ranges are virtually identical to the chart above. If a US brand lists their sizes in inches only, the same circumference numbers apply.

When in doubt, size up. Every wig cap has adjustable straps — it is always easier to take a wig in than to stretch one out.

FAQs

Q1: How do I know what size wig to buy in the UK?

Take a soft tape measure and wrap it around your head — start at the centre of your forehead, go above one ear, around the nape, above the other ear, back to start. If the number is between 21.5" and 22.5" (54–57 cm), you need an Average cap, which fits about 80% of UK women. Smaller heads (20.5–21.5" / 52–54 cm) take a Petite, larger heads (22.5–23.5" / 57–60 cm) take a Large. When in doubt, always size up — the adjustable straps inside every Ailsa's wig can take in up to an inch of slack.

Q2: What is the average UK wig size for women?

The UK average head circumference for adult women is around 22 inches (56 cm), which sits squarely inside the Average cap size range of 21.5"–22.5" (54–57 cm). Around 80% of our customers wear an Average. If you've never owned a wig before and you don't have time to measure, an Average cap is statistically your safest first choice — and you can always adjust the straps to fine-tune the fit once it arrives.

Q3: Can I adjust a wig that's too big or too small?

Yes, but only within limits. Every Ailsa's wig has adjustable straps at the nape that can take in roughly 1 inch (2.5 cm) of total slack — half an inch from each side. So a slightly oversized wig can be tightened down. A wig that's too small, however, cannot be made larger; the cap is woven from non-stretch material, and forcing it on will give you a headache and damage the wefts. This is why we always recommend sizing up if you're between two sizes.

Q4: Do I really need to measure my head before buying a wig online?

If you're buying your first wig, yes — it takes 30 seconds and removes most of the guesswork. If you've owned wigs before and you know you wear an Average cap, you can usually skip the tape measure. The exception is short wigs and bobs, where any cap sizing error is much more visible than on a long wig. For shorter styles we recommend re-measuring even if you're an experienced wig wearer.

Q5: What's the difference between Petite, Average and Large cap sizes?

The difference is purely circumference. Petite caps fit head circumferences of 20.5"–21.5" (52–54 cm), Average caps fit 21.5"–22.5" (54–57 cm), and Large caps fit 22.5"–23.5" (57–60 cm). The cap depth (front to nape and ear to ear) is also slightly smaller on Petite and slightly larger on Large, but the circumference is the main thing the manufacturer adjusts. Hair length, density, colour and style are all independent of cap size.

Q6: I have a high forehead — does that affect what wig size I need?

Not the cap circumference (Step 1), but it does affect the front-to-nape measurement (Step 2). If your forehead is unusually high, you may find that an Average cap sits a bit too far forward and ends up covering your eyebrows. The fix is to choose a wig with a lace front, which lets you pluck and shape the front edge to sit exactly where your natural hairline is, regardless of cap size.

Q7: Can I wear a wig if I have lots of bio-hair underneath?

Yes, but you'll usually need to size up by half a cap size and braid or pin your bio-hair flat against your scalp. A French braid or two flat cornrows works well; for shorter bio-hair, slick it down with gel and use bobby pins. The hair underneath adds bulk that the cap has to accommodate, so even if your bare-head circumference is 22" (an Average), wearing a wig over thick hair may push you into Large territory. If you'd rather skip the prep, try a headband wig, which is designed to sit over your existing hair without flattening it.

Next Steps — Find Your Perfect Wig

Now that you know your size, here's where to head next:

• For a beginner-friendly, no-glue option that just slips on, browse our glueless wigs collection.
• For the most natural-looking hairline you can pull back from your face, see our lace front wigs.
• If you'd rather not flatten your existing hair underneath, try a headband wig — no measuring or pinning required.
• For top-of-the-range natural hair you can wash, style and colour, explore our human hair wigs.
• Still not sure where to start? Read our complete guide on how to choose a wig for a step-by-step walkthrough, or browse every wig in stock.

And of course, if you'd like a real human to answer your questions, you can always call our Edinburgh store on 0131 664 7210 or book a free in-store try-on appointment at Cameron Toll Shopping Centre. Our styling team has been fitting wigs for over a decade — we love nothing more than helping someone find their perfect first wig.

Written by the Ailsa's Wigs Styling Team. Last updated 14 April 2026.