How much yarn do you actually need before you start a project?
UK yarn is sold by weight category, not by a fixed length, which is why two balls labelled "DK" from different mills rarely hold the same number of metres. A 100g ball of 4-ply typically runs 350-400m, double knitting (DK) around 200-230m, Aran nearer 150-170m, and chunky as little as 100-120m. Fibre content shifts these figures too: a wool-acrylic blend is usually lighter per metre than pure cotton.
The safest method is to work from the pattern's stated yardage and add a safety margin, ten percent is a sensible minimum for a jumper or blanket, since swatching, frogging and finishing all use extra yarn beyond the visible garment. Buy any extra balls in the same dye lot as your main stock; dye lots can differ enough in shade to show as a visible band across a finished piece.
How do you convert a crochet hook size between UK, US and metric?
The millimetre size stamped on the hook shaft is the only figure that stays constant everywhere, which makes it the reference point when a pattern's origin is unclear. US patterns label hooks with a letter-number pair such as H/8, and the mapping between letters and millimetres is not perfectly consistent between brands at the smaller and larger ends of the range.
Older British and Canadian patterns used a separate numbered system that runs in the opposite direction to the letters, a low number is a thick hook and a high number is fine, which trips up anyone working from a reprinted vintage leaflet. Guessing a substitute hook rather than converting properly changes stitch density enough that a garment can come out several centimetres off the stated size.
How much fabric do you need to buy for a sewing pattern?
The yardage printed on a pattern envelope assumes a specific fabric width, usually 112cm or 150cm, so switching to a narrower bolt than the envelope specifies means buying more length to fit the same pieces across it. Napped fabrics such as velvet and corduroy, and any print with an obvious direction, need every pattern piece cut facing the same way, which typically adds ten to twenty percent to the total.
Stripes, checks and large repeating prints add further, since seams have to line up, and each match point can cost a full pattern repeat in extra length. Buy for the cutting size on the envelope rather than your usual clothing size, and pre-wash a swatch of natural fibres before cutting since cotton and linen both shrink.
Why does a row counter matter for lace or cable patterns?
Plain stockinette forgives a lost place, every row looks the same, but lace and cable patterns repeat over blocks of several rows where each row is distinct. Missing where you are inside an eight-row repeat usually means unpicking back to the last point you can identify with certainty, which on a fine lace shawl can mean hours of work.
A mechanical clicker only tracks one number, so a chart with a row repeat nested inside a section repeat needs more than a single count. A digital counter that keeps several named tallies side by side, and remembers them if you put the project down for a few days, removes the guesswork when you pick the needles back up.