Bird Feeder Calculator

Cylinder volume depends on the square of the radius, so doubling diameter doubles the radius, and doubling a squared quantity roughly quadruples it — height alone scales volume proportionally, but diameter has a much stronger effect. This is why even a modest increase in feeder diameter can meaningfully extend how long a feeder lasts between refills compared to the same increase in height.

It's a general average across typical backyard bird species and isn't adjustable as a separate input, so it works best as a general planning baseline rather than a species-specific measurement. A yard dominated by larger birds like jays or doves will likely see somewhat higher actual consumption per visit than this average assumes, while a yard of mostly small finches may see somewhat less.

Denser seed packs more weight into the same feeder volume, so a feeder filled with a denser seed type holds more pounds and therefore lasts longer between refills at the same visit rate, even though the physical chamber size hasn't changed. Switching seed types without adjusting the density figure will understate or overstate how much seed a given feeder actually holds.

With no daily consumption to divide the feeder's capacity by, the calculator can't compute a meaningful number of days until empty, so it falls back to a large placeholder value representing effectively no consumption. In practice this scenario mostly matters for planning purposes — a real feeder with zero traffic isn't accomplishing its purpose regardless of how the math handles the edge case.