Tree Ring Mulch Calculator

By Vinod Kondeti · Updated October 14, 2026

A tree ring is a circle with a hole in the middle, because the mulch should not touch the trunk. Scotts says to keep mulch several inches away from tree trunks. Enter the ring size and the bare area at the trunk, and the calculator subtracts it.

Ring outer diameter (ft)Bare circle at trunk (diameter) (ft)Number of trees (trees)Depth (in)Extra for waste / settling (%)Bag size (ft³)

Cost estimate (optional, enter your local prices)

Price per bag ($)Bulk price per yd³ ($)Bulk delivery fee ($)

Cubic yards	–
Cubic feet	–
Cubic meters	–
Bags	–
Cost in bags	–
Cost in bulk (incl. delivery)	–
Cheaper option	–

Working: –

How do I measure for a tree ring project?

Outer diameter: measure across the whole ring, through the trunk.
Inner diameter: the trunk width plus the bare gap on both sides.
Set the number of trees for matching rings along a row.

How is the tree ring amount calculated?

Cubic feet = length × width × (depth in inches ÷ 12)
Cubic yards = ft³ ÷ 27
Bags = ft³ ÷ bag size (ft³), rounded up
One bag covers (bag ft³ × 12) ÷ depth (in) square feet; 1 yd³ covers 324 ÷ depth (in) ft²
Extra for waste/settling: volume × (1 + % ÷ 100)
Round bed: π × (d ÷ 2)²; tree ring: π ÷ 4 × (outer² − inner²)
Bulk cost = yd³ × $/yd³ + delivery; bag cost = bags × $/bag

Tree ring calculator questions

How much mulch for a 6 ft ring with a 1 ft bare centre, 3 in deep?

π ÷ 4 × (36 − 1) = 27.5 ft² × 0.25 = 6.87 ft³, about 4 bags of 2 cu ft before extra.

Why subtract the centre?

Mulch piled against the trunk is what Scotts advises against, and leaving that area out also stops you overbuying.

Sources

Estimates only. Use the coverage or bag size printed on your product. Read the mulch guide for worked examples.