How the Compost Converter Works
The Compost Converter divides compost mass by compost bulk density. The default 0.55 kg/L fits mature, moist compost.
Judge the compost
Fresh, mature, screened and dry compost differ in density.
Enter the density
Use the table value or weigh a level 10 L bucket.
Enter the mass
Type the compost weight in kilograms.
Read the volume
Divide the liters by bed area to find spread depth.
Compost Converter Formula
The compost formula is V = m ÷ ρcompost. Spread depth equals volume ÷ area.
- ρcompost
- Compost bulk density at its moisture, kg/L
Worked Examples
- Bulk bag: 500 kg ÷ 0.55 = 909 L (0.91 m³).
- Mulching 20 m² at 50 mm: 1,000 L × 0.55 = 550 kg of compost.
- 40 L retail bag: 40 × 0.55 = 22 kg.
Compost Converter Conversion Table
1 m³ of mature compost weighs about 550 kg (1,213 lb). The table lists 6 compost types with coverage per tonne at 50 mm.
| Compost Type | Density (kg/L) | lb per ft³ | m³ per tonne | m² per tonne at 50 mm |
|---|---|---|---|---|
| Dry screened compost | 0.400 | 25.0 | 2.50 | 50.0 |
| Fresh yard waste compost | 0.450 | 28.1 | 2.22 | 44.4 |
| Mature compost (moist) | 0.550 | 34.3 | 1.82 | 36.4 |
| Mushroom compost | 0.600 | 37.5 | 1.67 | 33.3 |
| Composted manure | 0.700 | 43.7 | 1.43 | 28.6 |
| Wet food waste compost | 0.800 | 49.9 | 1.25 | 25.0 |
What is a Compost Converter?
A Compost Converter is a calculator that converts compost weight into volume and spreading coverage.
Compost is organic matter broken down by microbes into a dark, crumbly soil amendment. Mature compost holds 40–60% water by weight, which sets most of its density.
Organic matter weighs far less than mineral soil. Compost particle density sits near 1.5 kg/L against 2.65 kg/L for sand and clay minerals.
What are the Uses of a Compost Converter?
There are 4 main uses of a Compost Converter.
Garden mulching
Gardeners convert bulk bags into spread depth.
Farm application
Farmers convert t/ha rates into spreader loads.
Municipal compost sales
Sites convert weighbridge tonnes into m³ sold.
Potting mixes
Growers blend compost into media by volume.