Work out wire delay (elmore) instantly with clear inputs, formula shown and shareable results.
The Elmore delay of a driven RC line is Rd(Cw + Cl) + Rw(Cw/2 + Cl). The factor of a half on wire capacitance reflects its distribution along the line. Multiplying by 0.69 (ln 2) converts the Elmore time constant to a 50% propagation delay.
Elmore delay
T = Rdriver(Cwire + Cload) + Rwire(Cwire/2 + Cload); t50 = 0.69 T
Charge nearest the driver sees less wire resistance than charge at the far end. Integrating along the line gives an average of half.
When wire resistance approaches driver resistance — typically for long thin wires on lower metal layers, which is why critical global nets are routed on thick upper metal.