Round Bed Mulch Calculator

By Vinod Kondeti · Updated October 14, 2026

Circular island beds look simple, but their area grows with the square of the diameter. An 8 ft bed is 50.3 ft², and a 12 ft bed is 113.1 ft². Enter the diameter and depth to get yards and bags.

Bed diameter (ft)Number of beds (beds)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 round bed project?

Measure the widest distance across the bed.
For an oval, use the average of its long and short diameters as an approximation.
Use the number of beds field for several beds of the same size.

How is the round bed 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

Round bed calculator questions

How much mulch for an 8 ft round bed at 3 in?

50.27 ft² × 0.25 = 12.57 ft³, which is 0.47 yd³ or 7 bags of 2 cu ft before extra.

Is a half-circle bed half the mulch?

Yes. Halve the result, or enter the full circle and divide by 2.

Sources

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