Hat sizes look confusing because the US system uses fractions (7 1/8, 7 1/4, 7 3/8), the UK uses different fractions, alpha sizes (S/M/L) overlap, and EU goes by metric. Our hat size calculator above converts between all of them instantly — just enter your head circumference in cm or inches, or any size you already know, and it returns every equivalent.
This guide covers the full hat size chart, what each fractional size means in inches and cm, how to size fitted caps (New Era), cowboy hats, fedoras, kids’ hats, and includes a printable measuring tape you can use without owning a soft tape measure.
How to use the hat size calculator
Open the calculator at the top of this page and choose what you know — head circumference in centimeters or inches, US fractional size (like 7 1/4), or alpha size (S, M, L). The tool returns all four conversion systems plus an indication of where you fall on the chart. Switch tabs for hat-type-specific sizing (fitted, cowboy, fedora, beanie), kids’ hat sizes, or the printable measuring tape.
Hat size chart — full conversion table
This is the standard hat size chart used by Lock & Co., Hats.com, Nike, and most major hat brands. US fractional sizes are mathematically derived from circumference in inches divided by π — so a 22-inch head ÷ π ≈ a size 7 hat.
| US | UK | Alpha | cm | Inches |
|---|---|---|---|---|
| 6 1/4 | 6 1/8 | XXS | 49.5–50.5 | 19.5–19.9 |
| 6 3/8 | 6 1/4 | XXS | 50.5–51.5 | 19.9–20.2 |
| 6 1/2 | 6 3/8 | XS | 51.5–52.5 | 20.3–20.6 |
| 6 5/8 | 6 1/2 | XS | 52.5–53.5 | 20.7–21.0 |
| 6 3/4 | 6 5/8 | S | 53.5–54.5 | 21.0–21.4 |
| 6 7/8 | 6 3/4 | S | 54.5–55.5 | 21.5–21.8 |
| 7 | 6 7/8 | M | 55.5–56.5 | 21.9–22.2 |
| 7 1/8 | 7 | M | 56.5–57.5 | 22.3–22.6 |
| 7 1/4 | 7 1/8 | L | 57.5–58.5 | 22.7–23.0 |
| 7 3/8 | 7 1/4 | L | 58.5–59.5 | 23.1–23.4 |
| 7 1/2 | 7 3/8 | XL | 59.5–60.5 | 23.4–23.8 |
| 7 5/8 | 7 1/2 | XL | 60.5–61.5 | 23.9–24.2 |
| 7 3/4 | 7 5/8 | XXL | 61.5–62.5 | 24.3–24.6 |
| 7 7/8 | 7 3/4 | XXL | 62.5–63.5 | 24.6–25.0 |
| 8 | 7 7/8 | 3XL | 63.5–64.5 | 25.0–25.4 |
How to measure your head for a hat
You need a soft tape measure (the kind tailors use) or a string and ruler. Wrap the tape around the widest part of your head — about 1 inch above your eyebrows and ears. Keep it level, snug but not tight. Read the number where the tape overlaps.
A few practical points that matter:
- Measure twice and average the two — small differences are normal
- Hair tied up vs. hair down can change your measurement by 1–2 cm; measure with your hair as you’ll wear it
- For headbands, use the smallest measurement; for hats, use the natural one
- Glasses don’t affect head circumference at the measurement line
No soft tape measure? Open the Print & Measure tab in the calculator — we have a printable measuring strip you can cut out and use.
Hat size in inches — what does my measurement mean?
In the US system, your hat size in fractional inches equals your head circumference in inches divided by π (≈ 3.14). For practical use, here’s the direct map:
- 21 inches = US size 6 3/4 (S)
- 21.5 inches = US size 6 7/8 (S)
- 22 inches = US size 7 (M)
- 22.5 inches = US size 7 1/8 (M)
- 23 inches = US size 7 1/4 (L)
- 23.5 inches = US size 7 3/8 (L)
- 24 inches = US size 7 5/8 (XL)
- 24.5 inches = US size 7 3/4 (XXL)
Hat size in cm — quick metric reference
For people using metric measurements:
- 54 cm = US 6 3/4
- 55 cm = US 6 7/8
- 56 cm = US 7
- 57 cm = US 7 1/8
- 58 cm = US 7 1/4
- 59 cm = US 7 3/8
- 60 cm = US 7 1/2
- 61 cm = US 7 5/8
- 62 cm = US 7 3/4
- 63 cm = US 7 7/8
Fitted hat size chart (New Era 59FIFTY, MLB caps)
Fitted hats — most famously New Era’s 59FIFTY line and official MLB on-field caps — are sold in exact fractional sizes only. They don’t stretch, so the fit has to be right. The conversion is the same as the standard chart above:
| Cap size | cm | Inches |
|---|---|---|
| 6 7/8 | 54.5–55.5 | 21.5–21.8 |
| 7 | 55.5–56.5 | 21.9–22.2 |
| 7 1/8 | 56.5–57.5 | 22.3–22.6 |
| 7 1/4 | 57.5–58.5 | 22.7–23.0 |
| 7 3/8 | 58.5–59.5 | 23.1–23.4 |
| 7 1/2 | 59.5–60.5 | 23.4–23.8 |
| 7 5/8 | 60.5–61.5 | 23.9–24.2 |
| 7 3/4 | 61.5–62.5 | 24.3–24.6 |
Most adult men fall in 7 1/4 to 7 5/8. Most adult women fall in 6 7/8 to 7 1/4. If you’re between sizes, go up — fitted caps loosen a tiny bit over the first few wears but don’t shrink, and a too-small cap is painful.
Cowboy hat / Western hat size chart
Western and cowboy hats — Stetson, Resistol, American Hat Co., Bailey — follow the same US fractional sizing as the standard chart. The fit just needs to be tighter than a regular hat because the brim is heavier and prone to falling off in wind.
Cowboy hat sizing tip: a quality hatter can steam-shape the crown slightly to adjust between sizes. If you’re between sizes and buying online, choose the smaller size; if you’re between sizes and visiting a Western shop, ask about steaming. Cowboy hats also benefit from a sweatband insert when sized half a size up, which fine-tunes the fit without sacrificing comfort.
Fedora and structured hat sizing
Structured hats — fedoras, panamas, bowlers, top hats — don’t stretch. The fit has to be precise from day one. If you’re between two sizes:
- Always go smaller, not larger — structured hats loosen 1–2 mm of equivalent fit over the first few wears
- Look for hats with an adjustable inner sweatband (some Goorin Bros and Bailey models include this)
- For permanent custom fit, a hatter can install a sweatband at the right size for $10–25
How to read New Era and brand size labels
New Era stamps the size inside the cap, under the sweatband, often in a label or sticker on the inside crown. The number you’ll see is the fractional US size (like “7 1/4”). Most other fitted-cap brands (Mitchell & Ness, 47 Brand, Lids, MLB authentics) use the exact same fractional system.
For Flexfit, Yupoong, and similar stretch-fit caps, the label shows a range (S/M or L/XL) instead. Match your measured size to the brand’s stated range — overlap is normal at the boundaries:
- Flexfit S/M ≈ US 6 3/4 to 7 1/4 (54–58 cm)
- Flexfit L/XL ≈ US 7 1/8 to 7 5/8 (57–61 cm)
- Flexfit XXL ≈ US 7 5/8 to 8 (61–64 cm)
Snapback and adjustable cap sizing
Snapbacks, dad caps, and velcro-back caps are sold as “one size fits most” — which usually means roughly US 6 5/8 to 7 5/8 (53–61 cm). If your head is outside this range, look for XL versions specifically marked. Adjustable caps don’t fit XS heads well (the strap won’t tighten enough) or XXL+ heads (won’t extend that far).
Kids and baby hat size chart
Kids’ heads grow extremely fast in the first two years — 60% of adult size at birth, 90% by age 2. Always measure if possible; age ranges are a backup.
| Age | Head circumference | US fractional |
|---|---|---|
| Newborn (0–3 mo) | 33–38 cm | – |
| 3–6 months | 38–43 cm | – |
| 6–12 months | 43–46 cm | – |
| 12–24 months | 46–48 cm | – |
| 2–3 years | 48–50 cm | 6 1/4 |
| 3–5 years | 50–52 cm | 6 1/2 |
| 5–8 years | 52–54 cm | 6 3/4 |
| 8–12 years | 54–56 cm | 7 |
| 12–14 years | 56–58 cm | 7 1/4 |
| 14+ years | 56–64 cm | adult sizing (7+) |
For newborns specifically, hospitals record head circumference at birth — that number is essentially the cm hat size. Most newborn beanies are labelled 0-3M and fit 33–38 cm.
Men’s vs women’s hat sizes — is there a difference?
In hat sizing, the system is identical for men and women — your head circumference determines your size regardless of gender. The differences are about average size and style availability:
- Average men’s head: 57–58 cm (US 7 1/8 to 7 1/4)
- Average women’s head: 55–56 cm (US 6 7/8 to 7)
Men’s hats are typically offered up to 8+ (XXL+); women’s-marketed hats often stop at 7 1/2 (XL) because of lower demand at larger sizes.
Welding hat, hard hat, and helmet sizing
Hard hats are sized by a different system — most use a continuous adjustable ratchet that fits 6 1/2 to 8 (52–64 cm). Construction-grade hard hats list this range on the shell. Welding hats (cloth caps worn under helmets) usually follow standard US fractional sizing.
Bike helmets and ski helmets are sized by head circumference in cm and grouped into S/M/L ranges — see the size guide on the specific helmet brand.
Brand-specific hat size charts
Most quality hat brands follow the same US fractional system but with slightly different fit characteristics:
- Stetson — true to size, runs slightly snug; structured hats expect 1mm of stretch over time
- Goorin Bros — true to size, often offers adjustable sweatbands inside their fitted styles
- Brixton — runs slightly small; consider sizing up half if between sizes
- Tilley — sizes by inches; their charts list both inches and cm
- Bailey — true to size, especially their Western line
- New Era / Mitchell & Ness — exact fractional, no stretch
- Nike, Adidas, Under Armour — typically alpha sizes (S/M/L) with cm ranges shown
When buying from any brand, check the specific product’s size chart on the brand’s website — small variations exist within the standard system.
FAQ section (single box)
How do I figure out my hat size?
Measure your head circumference with a soft tape measure (or string + ruler) wrapped around the widest part — about 1 inch above your eyebrows and ears. That measurement in cm or inches tells you your size: 57 cm = US 7 1/8, 22 inches = US 7. Use our calculator at the top of this page for an instant conversion to every system.
What is the average hat size for a man?
The average adult man’s head is about 57–58 cm (22.5–22.8 inches), which is US fractional size 7 1/8 to 7 1/4 (alpha M to L). About 70% of adult men fall between US 7 and 7 1/2.
What is the average hat size for a woman?
The average adult woman’s head is about 55–56 cm (21.7–22 inches), which is US fractional size 6 7/8 to 7 (alpha S to M). About 70% of adult women fall between US 6 5/8 and 7 1/4.
What is a 7 1/4 hat size in cm?
A US 7 1/4 hat size corresponds to a head circumference of 57.5 to 58.5 cm (22.7 to 23.0 inches). It’s the alpha size L and the UK equivalent 7 1/8.
What is a 7 1/8 hat size in inches?
A US 7 1/8 hat size fits a head circumference of about 22.3 to 22.6 inches (56.5 to 57.5 cm). It’s the alpha size M and the UK equivalent 7.
What is a 7 3/8 hat size?
A US 7 3/8 hat size fits a head circumference of about 23.1 to 23.4 inches (58.5 to 59.5 cm). It’s the alpha size L and the UK equivalent 7 1/4. It’s slightly larger than a 7 1/4 and slightly smaller than a 7 1/2.
What is a 7 1/2 hat size in cm?
A US 7 1/2 hat size fits a head circumference of 59.5 to 60.5 cm (23.4 to 23.8 inches). It’s the alpha size XL and the UK equivalent 7 3/8.
What is a 7 5/8 hat size in cm?
A US 7 5/8 hat size fits a head circumference of 60.5 to 61.5 cm (23.9 to 24.2 inches). It’s the alpha size XL and the UK equivalent 7 1/2.
What is a 6 7/8 hat size? Is that small?
A US 6 7/8 hat fits a head circumference of 54.5 to 55.5 cm (21.5 to 21.8 inches) — alpha size S. It’s smaller than average — slightly smaller than typical for women (who average 7) and significantly smaller than average for men. Common for petite frames, smaller-bone heads, or older children/teens.
What size hat for a 22 inch head?
A 22-inch head circumference fits a US 7 hat (alpha M, UK 6 7/8, EU 56). It’s right at the average adult-male size.
Should I size up or down for a hat?
It depends on the hat type. Fitted caps (New Era): size up if between — they don’t stretch. Structured hats (fedoras, panamas): size down — they loosen slightly with wear. Beanies and stretch caps (Flexfit): doesn’t matter much — they cover ranges. Cowboy hats: size precisely — they can be steam-adjusted at a hatter.
How do I measure a baby’s head for a hat?
Use a soft tape measure or a piece of string. Wrap it around the widest part of the baby’s head — about 1 inch above the eyebrows. Keep it level. Babies’ heads are often measured at well-child pediatrician visits, so you can also ask your pediatrician or check your child’s growth chart. Most newborns fit a 33–38 cm beanie (labelled 0-3M).
How is a hat size calculated?
US hat sizes are calculated from head circumference in inches divided by π (3.14159): a 22-inch head ÷ π ≈ 7, so it’s a size 7. Hat size in cm is the head circumference itself (a 57 cm head is roughly a 57 cm hat size). EU/metric hat sizes are the rounded cm value. The UK uses a fractional system offset by one-eighth from US: a US 7 is a UK 6 7/8.
What’s the largest hat size?
Most major brands stop at size 8 (US, 25 inches / 63.5 cm) in their standard line. Above that, custom hatters or specialist big-head retailers offer up to 8 5/8 (XXXL+). Mass retailers like Lids and New Era stop at 8 in fitted; adjustable caps cap out around 7 5/8 to 8.
What’s the smallest adult hat size?
Most adult hats start at size 6 1/2 (US, 51.5 cm). Below that, you’re typically in kids’ or youth sizing. Some women’s fashion lines stock 6 3/8 (50.5 cm) for petite heads.