F-5 Crochet Hook (3.75 mm): Yarn Weight, Gauge and Size Conversions
The F-5 hook is 3.75 mm. It suits fine (sport) yarn, which CYC gauges at 16 to 20 single crochet per 4 inches. At about 19 stitches per 4 inches, a 50 inch blanket starts with about 239 chains. A 20 inch hat band is about 95 stitches around.
Crochet hook size is the diameter of the shank, the smooth part of the hook that sets the size of each loop. This hook is 3.75 mm, about 0.15 inch across. The US label F-5 and the 3.75 mm size describe the same hook. Letters vary between brands, so the millimeter size is the one to match.
What is the F-5 hook in mm and UK sizes?
| Metric | 3.75 mm |
|---|---|
| Inches (shank diameter) | 0.15 in |
| US letter and number | F-5 |
| Old UK size | None |
| Knitting needle, same diameter | US 5 (3.75 mm) |
| Usual yarn weight | fine (sport) |
| Estimated gauge | about 19 single crochet per 4 in |
What yarn weight do you use with a 3.75 mm crochet hook?
The Craft Yarn Council lists 3.75 mm inside the recommended hook range for the weights below. The chain and hat columns show how far the full gauge range of each weight moves the stitch count.
| Yarn weight | CYC hook range | Single crochet per 4 in | Chain for 50 in | 20 in hat band |
|---|---|---|---|---|
| Fine (sport) | 3.5 to 4.5 mm (E-4 to size 7) | 16 to 20 | 201 to 251 | 80 to 100 |
What is the crochet chain length for a blanket with a F-5 hook?
The estimated gauge places 3.75 mm within the CYC hook range for fine (sport) yarn, giving about 19 single crochet per 4 inches. Each starting chain is the stitches needed for the width plus 1 turning chain for single crochet. Rows of taller stitches or lacy patterns change the width per stitch, so swatch in the stitch you plan to use.
| Blanket | Width (in) | Starting chain (estimate) |
|---|---|---|
| Stroller / Car Seat | 30 | about 144 |
| Receiving | 30 | about 144 |
| Baby / Crib | 42 | about 201 |
| Throw / Afghan | 50 | about 239 |
| Twin | 66 | about 315 |
| Full / Double | 80 | about 381 |
| Queen | 90 | about 429 |
| King | 108 | about 514 |
Chain loosely, or go up a size
Foundation chains are usually tighter than the rows above them, which makes the bottom edge pull in. Many crocheters chain with a hook one size larger, then switch back. Enter your own swatch in the crochet chain calculator for an exact count.
Hooks and supplies for a F-5 hook
Boye Metal Ergonomic Crochet Hook Set, F to I
$16.32Four aluminum hooks with grip handles in F (3.75), G (4.25), H (5) and I (5.25) mm.
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Boye Aluminum Crochet Hook Set, US D to K
$16.79Eight color-coded aluminum hooks from 3.125 to 6.5 mm, an inexpensive way to own every common size.
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Clover Amour Crochet Hook Set, 10 sizes
$47.17Ten sizes of soft grip handled hooks, a cushioned step up from bare aluminum.
Check pricePrices change often, so confirm on Amazon. As an Amazon Associate we earn from qualifying purchases.
What knitting needle size matches a F-5 hook?
A US 5 knitting needle is also 3.75 mm. For the same yarn, though, CYC pairs fine (sport) with 3.5 to 4.5 mm (E-4 to size 7) hooks, which run larger than the matching needles because crochet fabric is denser.
What are the crochet hook sizes next to the F-5 hook?
Frequently asked questions
What size is an F-5 hook in mm?
The F-5 hook is 3.75 mm across the shank, about 0.15 inch. Hook size is measured on the shank, the smooth section between the throat and the thumb rest, because that part sets the size of every loop. Letters and numbers vary between brands, especially at the large end, so the millimeter size stamped on the hook is the one to trust. The neighboring sizes are E-4 (3.5 mm) and G-6 (4 mm).
What yarn weight do you use with a 3.75 mm crochet hook?
CYC places 3.75 mm within the recommended hook range for fine (sport) yarn. Fine (sport) is the usual match, with a hook range of 3.5 to 4.5 mm (E-4 to size 7) and a gauge of 16 to 20 single crochet per 4 inches. It sits inside one category, so it is a straightforward match. Amigurumi often uses a smaller hook than the label for tight stitches.
How many chains do I need for a blanket with a F-5 hook?
At about 19 single crochet per 4 inches, our estimate for fine (sport) yarn on a 3.75 mm hook, a 50 inch wide throw starts with about 239 chains, including 1 turning chain. A 42 inch baby blanket needs about 201 and a 90 inch queen about 429. Foundation chains tend to be tighter than the rows above, so many crocheters chain with a hook one size larger.
Is there a UK size for a 3.75 mm crochet hook?
Common conversion charts give no old UK number for 3.75 mm. Current UK and European patterns use millimeters, so a pattern asking for a 3.75 mm hook means this exact size. Watch the stitch names as well as the hook: UK double crochet is the same stitch as US single crochet, and UK treble is US double crochet.
What knitting needle is the same size as a F-5 hook?
A US 5 knitting needle is also 3.75 mm. Same diameter does not mean same yarn: CYC pairs fine (sport) yarn with 3.5 to 4.5 mm (E-4 to size 7) hooks but 3.25 to 3.75 mm (US 3 to 5) needles, because crochet stitches are denser. For the same yarn, crocheters usually reach for a bigger tool than knitters.
Is a F-5 hook good for beginners?
It is better once you are comfortable with the basic stitches. At 3.75 mm the stitches are small, about 19 per 4 inches, so counting takes good light and patience. Thin hooks also encourage a tight grip, so a cushioned handle, bright daylight lamp and regular breaks help. Many beginners start on a 5 mm H-8 hook with worsted yarn.
How we research: we compare manufacturer specifications, owner manuals, published standards and recurring themes in verified owner reviews. We do not test products in person, and this is researched guidance, not professional advice. Follow your machine manual and pattern, and take care with rotary cutters, hot irons and needles. As an Amazon Associate we earn from qualifying purchases.