Practilia
Garden calculator

Mulch and Soil Calculator

Estimate mulch, soil, compost, or landscape rock by bags and bulk volume with US customary or metric units.

Unit system

Example values loaded. The result updates automatically when you edit bed size, depth, or package details.

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Area and depth

Choose what you are buying; the calculation uses volume.

Measure the longest length of the area you will cover.

ft

Use the average width; split irregular beds into sections.

ft

Use the depth you still need to add, not the total depth already in the bed.

in
Purchase and margin

Allowance for settling, uneven beds, spillage, and small measuring errors.

%

Use the volume printed on the bag.

cu ft

Use how your supplier rounds bulk orders, such as the smallest accepted increment.

cu yd

Inputs

Material
Mulch
Bed length
12 ft
Bed width
8 ft
Depth
3 in
Extra margin
10%
Bag size
2 cu ft
Bulk order increment
0.25 cu yd

How to interpret the result

After calculation, use the bag count when buying retail bags or hauling material in smaller loads. Use the bulk order when a supplier sells by cubic yard or cubic meter. The surplus after bags shows the extra volume created by rounding up to whole bags.

Common mistakes

  • Using area directly without multiplying by depth in the active unit system.
  • Forgetting that bagged material is sold by volume, while some bulk suppliers round to set increments.
  • Applying new material without checking the depth already present in the bed.

Method

Formula: area = length x width. Volume = area x depth. Adjusted volume = volume x (1 + extra margin / 100). Bags and bulk orders are rounded up from the adjusted volume.

Example

Reference examples: in US units, a 12 ft x 8 ft bed at 3 in deep with 10% extra gives 26.4 cu ft, 14 bags at 2 cu ft, and 1.00 cu yd in 0.25 cu yd bulk increments. In metric units, a 3 m x 2 m bed at 5 cm deep with 10% extra gives 330 L, 9 bags at 40 L, and 0.4 m³ in 0.1 m³ bulk increments.

Assumptions

The calculator uses rectangular sections. Split irregular beds into smaller rectangles and add the results. Bag counts are volume-based, not weight-based, and the extra margin can cover settling, uneven ground, spillage, and measuring error.

Review

Last reviewed: 6/24/2026

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