How do you calculate cost per metre of material?

Shops sell fabric per linear metre at a fixed roll width (often 140–150 cm). You pay for length, not area. Check width before buying — a "metre" of narrow ribbon differs from upholstery fabric.

Add 5–10% for bends, connections and mistakes. Electricians often round up to whole reel lengths. Measure the actual route, not straight-line distance on a plan.

Convert both to price per metre: total roll price ÷ metres in roll. A €48 roll of 6 m (€8/m) beats €55 for 8 m (€6.875/m) only if you need all 8 m.

Timber is sold both ways. Convert using cross-section: a 47×100 mm board at €X/m has a known volume per metre — compare like sections when shopping.