TCTopsoilCalc

Free garden compost calculator

Compost Calculator

Estimate how much compost you need for a garden bed, lawn topdressing or raised bed blend. Get cubic yards, cubic feet and bag count without signing up.

  • Choose the job. Apply a compost layer to an area or calculate compost as part of a raised bed mix.
  • Enter the dimensions. Use the inside area and the depth you plan to apply or fill.
  • Shop by volume. Compare cubic yards with the bag size printed on your product.

Calculate compost

Calculation mode
Measurement system

For garden beds, enter the layer you plan to apply. Use a smaller depth for lawn topdressing.

Compost needed
0.12 yd3
Cubic feet3.7
Bags needed5
Applied as100%

Includes 10% extra for settling. Bag count is rounded up.

How compost volume is calculated

The calculator finds the volume of your area and then applies either a settling allowance or a compost percentage. Use the product label for the final bag conversion because compost bags vary.

Area compost = length x width x depth
Raised bed compost = total bed volume x compost percentage
Bag count = compost volume / bag volume, rounded up
1 cubic yard = 27 cubic feet

Use compost for the right task

  • Garden beds: enter the surface layer you plan to apply and work it into the soil as appropriate for the bed.
  • Lawn topdressing: use a thin custom depth and confirm that existing grass will not be buried.
  • Raised beds: calculate a compost percentage instead of treating the whole bed as pure compost.
  • Bag shopping: check the label volume; a 40-liter bag is not the same as a 2-cubic-foot bag.

Continue planning your soil project

Compost is one part of a soil purchase. Use the related tools for total bed volume, lawn depth, pots and delivered cost.

Soil Volume CalculatorCalculate total volume for a garden bed or soil area. Raised Bed Soil CalculatorPlan a complete topsoil, compost and aeration mix. Lawn Topsoil CalculatorChoose a project depth for topdressing, sod or new grass. Potting Soil CalculatorEstimate liters and bags for round or tapered pots. Topsoil Cost CalculatorCompare bulk delivery with bagged soil prices. Mulch CalculatorEstimate mulch cubic yards, bags and coverage for landscape beds. Gravel CalculatorEstimate landscape gravel cubic yards, tons and bags. Sand CalculatorEstimate paver, sandbox and landscape sand volume and bags. Topsoil CalculatorEstimate cubic yards, bags and tons for topsoil.

Compost calculator FAQ

How much compost do I need for a garden bed?

Multiply the bed area by the compost layer depth, then convert the volume to cubic feet or cubic yards. Use the bag size printed on your product to calculate bags.

How much compost should go in a raised bed?

Use the raised bed blend mode and enter the percentage you want to include. This shows the compost portion without pretending the whole bed is pure compost.

Can I use this for lawn topdressing?

Yes. Use the area mode with a thin custom depth, then confirm the depth for your grass and avoid covering the existing lawn too deeply.

How many bags of compost equal a cubic yard?

One cubic yard is 27 cubic feet. Divide 27 by the bag volume and round up; for example, 0.75-cubic-foot bags require 36 bags before any extra allowance.

Does this calculate a compost pile or carbon-to-nitrogen ratio?

No. This page calculates compost used as a soil amendment. Compost pile volume, decomposition yield and carbon-to-nitrogen ratios are different tasks with different inputs.