Mulch calculator.

Drafted to scale · cited sources · honest numbers

Enter the bed dimensions and depth. The calculator returns cubic yards, bag count, and cost for both bulk delivery and bagged mulch. Fires a hard warning when depth exceeds 4 inches (the tree-killing mulch-volcano threshold).

◈ DRAFTING PANEL · MULCH TAKEOFF · N.T.S. SHEET M-001 · REV A

Redline · scope notice Landscape mulch only (shredded wood, bark, hardwood). Does not compute playground surfacing to ASTM F1292 critical fall height. Rubber mulch and decorative rock have different volumes per bag and are not covered.

Note 01 · Field Procedure

How to measure the bed

Measure the longest dimension of the bed in each direction. For curved beds, approximate with the smallest rectangle that contains the shape, then subtract roughly 20% for the curves.
Decide on depth before ordering. New beds: 3 in. Refreshing existing mulch: 1.5-2 in. over what remains. Adding more than 4 in. total depth risks crown rot on trees and shrubs.
Check existing mulch depth with a ruler pushed to the soil line. Subtract that from the target depth. Over-mulching year after year is the #1 cause of landscape plant decline.
Keep a 3-6 in. gap between mulch and tree trunks, foundation walls, and wood siding. Mulch piled against wood accelerates rot and invites termites.

Note 02 · Equation

The formula

yd³ = L × W × d ÷ 324 × ( 1 + waste ÷ 100 )

Lbed length in feet

Wbed width in feet

dmulch depth in inches

324ft²·in → yd³ factor (12 × 27)

Note 03 · Sanity Ranges

Mulch by project size

T	Use case	Notes
50 sf	Tree ring	3 in. depth: ~0.5 yd³, 7 bags (2 cu ft). One wheelbarrow load.
100 sf	Small bed	3 in. depth: ~0.9 yd³, 13 bags. One bulk-delivery minimum.
200 sf	Foundation planting	3 in. depth: ~1.9 yd³, 25 bags. Bulk delivery is cheaper above 2 yd³.
500 sf	Large landscape	3 in. depth: ~4.6 yd³, 63 bags. Bagged at this volume costs 2-3x bulk.
1000+ sf	Full property	3 in. depth: ~9.3 yd³. Always bulk at this scale.

Note 04 · References

Sources

Authorities cited on this sheet

Clemson University HGIC 1604: Mulch · Clemson Cooperative Extension. Recommends wood and bark mulches at 2 to 3 in. depth and advises keeping mulch 2 to 3 in. away from the stems of woody plants; do not pile against the trunk. Primary reference for the volcano warning. Does not publish bag sizes or a settlement percentage.
Penn State Extension: Mulching Landscape Trees · Penn State Cooperative Extension. Confirms finely shredded mulches decompose faster and require more frequent replenishment. Does not quantify a year-one volume-loss figure; the 25 percent settlement constant in the calculator is a landscape trade rule-of-thumb, not a PSU value.
International Society of Arboriculture: Proper Mulching · ISA consumer guide. Covers the 2-4 in. depth standard, mulch-volcano damage, and the 6 in. trunk-clearance rule. Industry-standard reference for proper mulching technique.

PROJ MATERIALFOREMAN

SHT M-001 / 014

REV A · 2026-04-19

DRAWN MF