How to use the chart, and why sizes clash
Convert a bed size: choose the country and the name on your bed or mattress. You see its size in both units, the bedding usually sold for it there, and the closest mattress in each other system. "Same size" means within 3 cm both ways, close enough for fitted sheets; "close" means within 8 cm, where a stretchy sheet may fit and a tailored one may not. Those thresholds are our own rule of thumb.
Will it fit: pick a mattress (or type its size), its depth, and a duvet or flat sheet. A duvet should hang past each edge by at least the mattress depth, or the sides show. A flat sheet needs enough left over to tuck under; we assume a 25 cm (10 in) fold-back at the head and call a tuck under 10 cm (4 in) shallow.
Why names mislead: a UK king (150 × 200 cm) is close to a US queen, while a US king is 193 cm wide. Continental Europe names beds by width in centimetres; Australia's queen is 153 cm wide, New Zealand's king about 165 cm. Duvets differ too: German shops sell 135 × 200 cm singles, Swedish ones 150 × 200 cm, and French shops write the same duvet as 220 × 240 or 240 × 220.
Sizes vary: standards allow small tolerances, UK sizes are imperial at heart, and every maker cuts bedding a little differently. Use this chart to choose, then check the product's own dimensions.