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MATERIAL CALCULATOR

Compost calculator.

Estimate compost for a surface layer or a soil blend using your chosen proportions.

KEEP YOUR PLAN

Give your project a name.

Save your measurements and quotes on this device. No account needed.

My saved projects

YOUR MEASUREMENTS

Use the depth and allowance from your project specification.

Bag sizes, weight & pricing +

Bag counts and prices apply to the main material only. Enter your supplier’s density to calculate weight.

Compare bags with bulk delivery +

Use the bag size and units above. Compare the same product at your supplier’s quoted prices. Enter small-bag contents above and its price below. Include each delivery charge; enter zero for pickup.

Bulk-bag quote · optional third option

Compare small bags, bulk bags and a loose load side by side. Each price is optional; include delivery once for each option.

Minimum and increment use the bulk quote unit. For half-yard orders, enter 0.5 as the increment. Zero uses the exact estimate. Check taxes, unloading charges and access separately. Weight quotes need your supplier’s bulk density.

Your soil blend +

Enter two materials and their percentages if you want to calculate a blend. Choose the proportions for your planting plan.

Gouache illustration of a timber raised bed with soil, leafy plants and terracotta pots.
AI-generated illustration, not a photograph of a completed project.
BEFORE YOU ORDER

Getting a useful estimate

Choose the amount appropriate for your planting plan. No compost percentage is prescribed.

Measure the space you need to fill. Rectangles use length and width; circles use diameter. For several sections, choose combined areas and add rectangles, then subtract exclusions. The final area must be greater than zero.

Calculate compost for a layer or blend

For a surface application, enter the area and the compost depth you plan to add. For a blend, enter the total fill volume and your proportions. The two percentages must add up to 100.

University of Maryland Extension describes compost as a soil amendment. This tool estimates quantity. It does not interpret a soil test or recommend an application rate.

University of Maryland Extension: How to Make Compost at Home

Volume formula

Volume = area × depth × (1 + allowance ÷ 100)

Allowance applies once to each volume layer. No density or compaction factor is assumed. If buying by weight, enter the density for your supplier’s product in the units shown.

A worked example

An example 10-foot by 4-foot rectangle filled 1 inches deep needs 3.333 cubic feet, or 0.123457 cubic yards, without allowance. A 10% allowance gives 4 cubic feet. These are arithmetic examples, not recommended depths.

Calculate a two-component blend

Use internal bed or container measurements and the remaining depth to fill. An optional blend divides the total between two components at percentages you supply. The percentages must total 100. Full bags round up and may leave extra material.

Buying and checking quantities

Enter the volume printed on a bag, or its mass alongside supplier density. Counts round up to full bags. Costs use the purchasing unit and price you enter. Delivery is separate; labor and installation are outside this estimate. Copy or print your list to check with your supplier.

Sources & what they cover

  • NIST SI conversion factorsNational Institute of Standards and Technology

    Exact US customary and SI conversion factors; no material or installation recommendations.

    Source checked
  • How to Make Compost at HomeUniversity of Maryland Extension

    Compost as a soil amendment; no nutrient prescription or mixing ratio imported.

    Source checked

We check what each reference covers. A source check does not mean a specialist has reviewed this tool. You supply the depths, densities, prices and blend proportions.

Operated by Pete CallaghanUpdated Not yet independently reviewedHow we check our toolsReport a correction