How to measure
Use these guides to identify the measurements the calculator needs. Drawings are not to scale.
Triangle: A is the base; B is height at a right angle to that base, not the sloped side.
Circle: D is the diameter through the center, not the radius.
Check the unit beside every field. For example, 10 ft 6 in is 10.5 ft. A layer depth may use inches while length uses feet.
From a garden bed to a shopping list
Choose the bed shape, enter its measurements and the depth you want to add, then check the volume printed on the bag. If you already measured the area, select I know the area. The answer includes both loose volume and whole bags, so you can compare bulk delivery with bagged mulch.
For a 10 × 10 ft bed at 3 inches deep, the measured volume is 25 cubic feet. With 10% extra it becomes 27.5 cubic feet, or about 1.02 cubic yards. That takes 14 bags of 2 cubic feet. The example button fills in these numbers.
How it works
Area multiplied by depth gives volume. Convert inches to feet by dividing by 12, then divide cubic feet by 27 for cubic yards. For a circle, area is π × (diameter ÷ 2)². For a triangle, it is base × perpendicular height ÷ 2.
The calculator adds your extra percentage before dividing by bag volume. It rounds up only the final bag count, using the full precision of the measurement behind the displayed result. Metric inputs use meters and centimeters; bag volume is in liters.
Before buying mulch
The initial 3-inch depth, 2-cubic-foot bag, and 10% extra are editable example settings. They are not recommendations for every bed. Measure the new layer you need, not the combined depth of old and new mulch. Avoid treating weight on a bag as its volume: moisture and material change that relationship.
For several beds, adding their unrounded volumes before rounding bags can avoid buying an extra partial bag for every bed. Very small positive volumes display as “<0.01” instead of a misleading zero. Dimensions, depth, and bag volume must be positive decimals; extra can be 0–100%.