Mulch & Gravel Calculator

What this calculation does not cover

• The covered area is one rectangle: `areaLength * areaWidth` and nothing else, so a curved border, a kidney-shaped bed, a circular tree ring or a path that turns a corner has to be broken into rectangles and each piece run separately before you add the yardages up. Each of those two fields also stops at 50 m (about 164 ft), and a longer run is clamped back to that bound rather than calculated.
• The depth you enter is spread flat across the whole measured area. Nothing thins the layer back from stems and trunks, dishes it around a drain cover or manhole, crowns a gravel path so it sheds water, or subtracts the mulch already sitting in the bed — the answer is a full new layer at the stated depth over the whole rectangle, and the depth field itself is capped at 12 inches (30.5 cm), so a deeper gravel fill is not what this describes.
• No material is named anywhere in the arithmetic, so shredded bark, wood chip, pea gravel, crushed stone and screened topsoil all come back as exactly the same volume. Bulk aggregate is normally sold and delivered by weight while mulch is sold by volume, and turning this volume into a weight for a gravel order needs a density figure the page never asks for.
• The "Extra for Settling" percentage is a single flat multiplier on the finished volume, capped at 25 per cent, and settling is what it is named for: mulch sinking and an uneven base. It is not a compaction allowance, so gravel that will be raked and plate-compacted to a finished depth needs more loose material delivered than the area-by-depth figure suggests, and nothing in the formula adds it.
• The figure comes back unrounded, at whatever fraction of a bulk unit the geometry gives. Bulk suppliers deliver in whole units of their own measure, by weight or in bulk bags and bagged mulch comes in fixed bag sizes, so this is the amount needed to cover the bed rather than the amount you can actually order — round up to the next unit your yard sells.
• Cost, where you switch it on, is applied through one installed-mulch rate per cubic yard for every result. Gravel, decorative stone and topsoil are priced at that same mulch rate, so the money figure tracks the volume correctly but not the material.