Compost Calculator
Top-dress lawns or amend beds with compost. The default 2 in depth matches a light surface application; increase depth for new beds.
Formula example
A 100 ft² lawn at 2 in deep, with 10% waste and compost at 40 lb/ft³ needs 0.68 yd³ to buy (18.33 ft³). That is about 0.37 US tons, 733 lb, and 10 bags at 2 ft³ each. Many suppliers round bulk orders to the next 0.5 yd³, which would be 1.00 yd³ on this job.
Material densities
Default dry densities come from published soil and aggregate references. You can override density in the calculator when your supplier quotes a different number.
| Material | lb/ft³ | ton/yd³ |
|---|---|---|
| Compost | 40 | 0.54 |
Top-dress versus incorporation
A 2 in surface application improves soil biology without burying turf crowns. If you will till compost into a new bed, increase depth and consider pairing with the topsoil calculator for the mineral fraction.
Moisture and density
Compost straight from a windrow can be heavier than bagged, cured product. Weigh a sample or use the supplier’s lab density when ordering by the ton.
FAQ
How much compost does a 2 in top-dress use?
Volume is net area times depth in feet, plus your waste percentage. The default 100 ft² lawn at 2 in with 10% waste is 0.68 yd³ to buy.
Why is 40 lb/ft³ the default density?
Finished compost varies by moisture and feedstock; 40 lb/ft³ is a widely cited consensus value in landscape references. Override it when your supplier provides a certified analysis.
Why are bag counts rounded up?
Partial bags are not sold at retail. After waste is included, the engine divides by bag volume and rounds up—10 bags on the default example at 2 ft³ each.
How do pounds relate to yards on this job?
Pounds come from purchase cubic feet times density. The same default case shows about 733 lb alongside 0.68 yd³.
Can I use this for mulch instead?
Use the mulch calculator for bark products with different settling rules and typical depths. This page keeps compost-specific defaults and densities.
Related tools
By Home Yard Calc Editorial Team · Sources listed on the methodology page · Last updated October 26, 2026
Estimates only. Densities, coverage and salt targets vary by product, moisture and manufacturer. Confirm with your supplier or equipment manual. Not a substitute for professional design, soil engineering or pool service.