THE MATH, MADE VISIBLE
How it works
Bed area × depth in feet = cubic feet. Multiply by (1 + allowance ÷ 100), divide by 27 for cubic yards, then divide by the printed bag volume and round up.
Real project examples
Two hundred square feet
20 × 10 ft at 3 in deep = 50 ft³. With 10% extra, order 55 ft³, or 2.04 yd³. Buy 28 bags of 2 ft³; package rounding adds 1 ft³.
Refreshing a smaller bed
12 × 4 ft with a 1 in top-up needs 4 ft³. With no extra allowance, two 2 ft³ bags cover the measured volume.
Before you buy
- Measure the additional layer you actually need. Existing mulch may make a full new layer unnecessary.
- Bag volume varies. Read the label instead of assuming every bag contains two cubic feet.
- Extension guidance commonly discusses 2–4 in layers, but appropriate depth depends on the plants and material. Keep mulch clear of trunks and avoid piling it against stems.
Questions worth asking
Is a yard the same as a cubic yard?
In a bulk mulch quote, “a yard” usually means one cubic yard: 27 cubic feet. Confirm the supplier’s sold unit.
Does the type of mulch change the volume formula?
No. Shape and depth determine geometric volume. Material and settling can change the practical allowance and appropriate depth.
Are bulk orders always cheaper?
No. Compare your own bag quote with bulk price plus delivery and minimum order. This tool does not assume local prices.
Sources & assumptions
NIST · unit conversion factorsUniversity of Minnesota Extension · mulch guidanceLast reviewed October 1, 2026. Planning defaults are editable examples. Product labels and supplier information override them.