Planting Hole Backfill Calculator

Planting Hole Backfill Calculator

Once a tree or shrub's root ball is positioned in its planting hole, how much backfill soil do you actually need to fill the remaining space? This calculator does that volume math.

Hole Volume = π × (Radius in ft)² × Depth in ft
Backfill Needed = Hole Volume - Root Ball Volume

Example

A 36" diameter, 18" deep hole with a 3 cubic ft root ball:

Hole Volume = 10.6 cu ft → Backfill Needed = 7.6 cu ft

Sizing the Hole Correctly First

A properly sized planting hole should typically be dug 2-3 times wider than the root ball, but no deeper than the root ball's actual height - planting too deep is one of the most common causes of poor establishment and eventual tree or shrub decline, since it can smother the root flare and encourage rot.

What Goes Into Backfill

Backfill soil is often blended with compost or other soil amendments to improve drainage and nutrient availability around the new root system, though many arborists now recommend backfilling primarily with the original excavated soil rather than heavily amended soil, since an overly rich planting hole can discourage roots from spreading beyond it into the surrounding native soil.