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Estimate how many US gallons and liters a vertical drum-style rain barrel can hold from inner diameter, inner height, and a fill percentage that leaves room for overflows, inlets, and air gap.
Last updated: April 17, 2026
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Inside the barrel wall, not the rim lip.
Usable vertical depth you intend to fill.
Use less than 100% if you leave air space for an overflow or inlet hardware.
US gallons
50.0 gal
Liters
189.1 L
Volume (ft³)
6.68 ft³
Volume (in³)
11,541 in³
Planning notes:
Geometry
V = π (d/2)² h
Gallons
231 in³ = 1 US gal
Practical planning
V × fill %
22 in inner diameter, 33 in inner height, 92% fill — about:
50.0 US gal
(189.1 L, 6.68 ft³)
The tool computes the volume of a right circular cylinder using your inner diameter and inner vertical height. It multiplies that volume by your fill percentage to approximate stored water when you do not brim-fill the drum. Results are shown in US liquid gallons, liters, cubic feet, and cubic inches.
cubicInches = π × (d/2)² × h × (fillPercent / 100)usGallons = cubicInches / 23111,541 in³
Compare to manufacturer specs or weigh-fill tests when available.
Share it with gardeners sizing rainwater drums and irrigation top-ups.
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