Rain Chain Length Calculator

About this calculator

A rain chain is a traditional Japanese alternative to an enclosed downspout — called kusari doi — that guides roof runoff visibly down a chain of linked cups or links instead of hiding it inside a pipe. Sizing one correctly just means matching its length to the vertical drop from the gutter outlet to the ground (or to a collection basin), with a little extra allowed for how the chain naturally hangs.

This calculator takes that drop height and the number of chains you're installing, then adds 5% slack to account for the fact that a hanging chain doesn't sit perfectly straight and needs a bit of extra length to reach its intended endpoint without stretching taut. It's a practical sizing tool for homeowners and landscapers planning gutter alternatives, rain gardens, or decorative water features around a home's roofline.