Get a thick aluminum ruler

The durable ruler answer is simple: buy a thick aluminum one, or stainless steel if you want the last ruler you ever buy.

Plastic rulers are junk. The cheap clear ones bend, warp, and eventually crack at the 15 cm mark. Wood looks nice but splits and swells if it gets damp. Both are fine if you’re measuring once a month. If you actually use a ruler, get metal.

Aluminum is the sweet spot. It’s stiff enough that a 30 cm piece won’t flex, light enough to carry, and thick enough to survive being dropped. Look for one that’s at least 2 mm thick — the thin ones from the dollar store bend just like plastic. Brands like Alumicolor and Westcott make good ones. The trick is the profile: a flat, one-piece extrusion with no riveted parts. Any joint will eventually loosen.

Stainless steel is stronger but heavier and has sharp edges. It’s overkill unless you’re using it as a straight edge for heavy