How do I convert yarn weights for substitution?

To substitute yarn weights, compare the yards-per-100g ratio. If switching from worsted (approx 200 yd/100g) to DK (approx 250 yd/100g), you'll need about 25% more yardage. Always make a gauge swatch with the new yarn to verify stitch count matches the pattern requirements.

What is the difference between yarn weight numbers?

The Craft Yarn Council's standard weight system ranges from 0 (lace) to 7 (jumbo). Each number represents a thickness category: 0=Lace, 1=Fingering, 2=Sport, 3=DK, 4=Worsted, 5=Bulky, 6=Super Bulky, 7=Jumbo. Higher numbers mean thicker yarn.

How do US and UK yarn weights compare?

US Fingering = UK 4-ply, US Sport = UK 5-ply, US DK = UK DK/8-ply, US Worsted = UK Aran/10-ply, US Bulky = UK Chunky. The weight names differ but the thickness categories align closely when comparing by wraps per inch (WPI).

What happens if I use the wrong yarn weight?

Using heavier yarn makes the item larger and stiffer; lighter yarn makes it smaller and drapier. For garments, wrong weight means wrong fit. For blankets, it means wrong dimensions. Always swatch first when substituting — gauge is the equalizer that lets any weight work.

Yarn Weight Converter: Substitute Any Yarn Weight Accurately

Name: Yarn Weight Converter
Author: Sarah Mitchell

📅 Last updated: February 2026

Sarah Mitchell

CYC Certified Instructor · 20+ Years Crochet Experience

Yarn substitution is one of the most common questions I get. This converter uses the Craft Yarn Council's standard weight system to give you precise adjustments every time.

✅ Fact-Checked📋 Editorial Standards

🎯 Key Takeaway: When substituting yarn weights, the critical adjustment is yardage. Heavier yarns need fewer yards; lighter yarns need more. Convert using the yards-per-100g ratio, then swatch with the adjusted hook size to match the pattern's gauge.

Finding the perfect yarn for a pattern is an art — and sometimes the exact yarn specified isn't available, is discontinued, or simply not in your budget. That's where yarn weight conversion becomes essential. Whether you're substituting DK for worsted, converting a fingering-weight shawl pattern to sport weight, or figuring out how much extra yarn you'll need when moving up or down a weight category, this calculator handles the math instantly.

The Craft Yarn Council defines 8 standard yarn weight categories, from ultra-fine lace (weight 0) through jumbo (weight 7). Each weight has a typical yards-per-100g range, a recommended hook size, and an expected gauge in stitches per 4 inches. When you switch between weights, all three of these change — and ignoring any one of them leads to a project that's the wrong size, the wrong drape, or both. I've learned this the hard way more times than I care to admit.

Our yarn weight converter uses the standard yards-per-100g ratios to calculate exactly how much yarn you need when switching weights. It also recommends the adjusted hook size and tells you how your gauge should change. Enter your original yarn weight, target weight, and the yardage from your pattern, and let the converter do the rest.

Convert Yarn Weight

Original Yarn Weight

Target Yarn Weight

Original Pattern Yardage (yards)

Conversion Results

—

Adjusted Yardage

—

Yardage Change

—

Original Hook

—

New Hook Size

—

Original Gauge

—

Target Gauge

💡 Critical: Always make a gauge swatch with your target yarn and the recommended hook size. Yarn weight conversion gives you a starting point — your personal tension determines the final hook choice.

Complete Yarn Weight Reference Chart

The Craft Yarn Council's Standard Yarn Weight System classifies all yarns into 8 categories. This chart shows the official specifications for each weight, including the US/UK terminology, typical yardage, hook sizes, and gauge ranges. Bookmark this page — you'll reference it constantly when substituting yarn.

#	US Name	UK/AU Name	Yd/100g	Hook Size	Gauge (st/4")	WPI
0	Lace	1-ply, Cobweb	800+	1.5–2.25mm	32–42	30+
1	Fingering / Sock	4-ply	400	2.25–3.5mm	21–32	14–17
2	Sport	5-ply	300	3.5–4.5mm	16–20	12–14
3	DK / Light Worsted	8-ply / DK	250	4.5–5.5mm	12–17	11–12
4	Worsted / Aran	10-ply / Aran	200	5.5–6.5mm	11–14	9–10
5	Bulky / Chunky	12-ply / Chunky	130	6.5–9mm	8–11	7–8
6	Super Bulky	Super Chunky	75	9–15mm	5–9	5–6
7	Jumbo / Roving	Jumbo	45	15mm+	3–5	1–4

Yarn Substitution Tips from 20 Years of Experience

Always swatch. I know, I know — every crochet article says this. But when substituting yarn weights, it's genuinely non-negotiable. The yardage conversion gives you the math, but your personal tension, the yarn's fiber content, and the specific stitch pattern all affect the final gauge. Two minutes of swatching saves hours of frogging a sweater that doesn't fit.

Fiber content changes drape. Converting from a cotton DK to a wool DK changes more than just the feel — cotton has zero elasticity and creates a stiffer fabric, while wool stretches and bounces back. If you're switching fibers at the same time as switching weights, make a larger swatch (at least 6×6 inches) to get an accurate gauge reading.

Going up in weight = go up in hook. If you're substituting bulky yarn for worsted, increase your hook size by 1–2 full sizes (e.g., from 5.5mm to 8mm). Going down? Decrease accordingly. The hook size chart above gives you the recommended starting point, but your swatch determines the final choice.

Holding double is a power trick. Can't find the right weight? Hold two strands of thinner yarn together. Two strands of fingering ≈ sport weight. Two strands of DK ≈ worsted. Two strands of worsted ≈ bulky. This opens up massive color mixing possibilities too — imagine one strand of solid navy with one strand of variegated blue-green.

Frequently Asked Questions

How do I substitute yarn weights?

Compare the yards-per-100g ratio between your original and target yarn. Use our converter above to calculate adjusted yardage, then match the hook size to the target weight and swatch to confirm gauge. The key equation is: New Yardage = Original Yardage × (Original yd/100g ÷ Target yd/100g).

Can I use DK yarn instead of worsted?

Yes. DK is one step lighter than worsted. You'll need about 25% more yardage (DK is ~250 yd/100g vs worsted at ~200 yd/100g), and you should go down 1 hook size (e.g., 4.5–5mm instead of 5.5–6.5mm). The finished item will be slightly thinner and more drapey.

What is WPI and how do I measure it?

WPI stands for Wraps Per Inch. Wrap yarn around a ruler or WPI tool without stretching or overlapping, then count the wraps in one inch. Higher WPI = thinner yarn. Worsted typically measures 9–10 WPI, DK is 11–12 WPI, and bulky is 7–8 WPI. It's the most reliable way to identify unlabeled yarn.

What happens if I use the wrong weight?

Using heavier yarn without adjusting hook and stitch count makes items larger, stiffer, and uses more yarn. Using lighter yarn makes items smaller and drapier. For blankets this might be tolerable, but for garments, wrong weight means wrong fit. Always swatch to the pattern's gauge.

Can I hold two strands together instead?

Yes! Holding double is a great substitution technique. Two strands of fingering ≈ sport. Two strands of DK ≈ worsted. Two strands of worsted ≈ bulky. Swatch to verify gauge, as the result varies by fiber type and tension.

📚 Sources & References

Craft Yarn Council — Standard Yarn Weight System
Ravelry — Yarn Weight Database & Community Comparison Data
Clara Parkes — "The Knitter's Book of Yarn" (Potter Craft, 2007) — Fiber property reference
Interweave — "Understanding Yarn Substitution" Technical Guide