Strength for weight, on one scale

Steel is strong. So is spider silk. But "strong" hides a second question: strong for how much weight? Specific strength answers it by dividing a material's tensile strength by its density, so a light fiber and a dense metal finally sit on the same axis.

Strength Stack is a chart you build by hand. Drag a material from the tray onto the plot and every bar rescales and re-sorts around it, so you can watch steel shrink the moment carbon fiber lands above it. Start from the three seeded materials, add the other nine in any order, and remove any of them to compare a smaller set.

Questions

What is specific strength?: Tensile strength divided by density, measured here in kN·m/kg. It tells you how much load a material carries for its weight, which is why engineers reach for it when weight is the constraint: aircraft, bikes, prosthetics, rockets.
Is spider silk really stronger than steel?: For its weight, yes. Dragline spider silk lands well above hardened steel on the specific-strength axis, because silk is far lighter for the pulling force it survives. By raw force alone, steel still wins.
What comes out on top?: The synthetic fibers. Kevlar 49 and carbon fiber rank highest by weight. Snail teeth (limpet radula) is the strongest natural material by raw tensile strength, but it is dense enough that the fibers still beat it once weight is accounted for.
Where does the data come from?: Typical, representative figures for each material class, drawn from standard materials-science references. Real values shift with grade, processing, and test method, so treat this as a tool for comparison, not for engineering design.
Do I need an account?: No. Strength Stack runs entirely in your browser, works on a phone with tap or drag, and stores nothing except whether you have muted the sound.