Plan amendment quantities for lawns, beds, pads, and backfills with confidence now. Compare compost, topsoil, and blends, including costs, bags, and waste factors easily.
| Project | Area | Depth | Method | Amendment Needed | Cost Estimate |
|---|---|---|---|---|---|
| Planting bed | 200 ft² | 6 in | 15% mix | 1.38 cu yd | $48.30 |
| Lawn topdress | 500 ft² | 2 in | 10% mix | 1.03 cu yd | $36.05 |
| Raised bed fill | 12 m² | 20 cm | Organic target | 0.65 m³ | $42.25 |
Area depends on your chosen geometry:
Soil volume is:
Amendment volume uses one of two approaches:
Loss factors adjust the final quantity:
Weight uses bulk density:
On pads and landscaped edges, soil amendments can improve water retention, compaction behavior, and plant establishment. Keep organic materials away from structural subgrades unless the specification allows them.
For engineered backfill, consult the geotechnical report before blending any organics. Use field moisture control and lift thickness to avoid settlement and soft spots.
Healthy topsoil supports vegetation, reduces erosion, and improves infiltration around hardscapes. A thin, compacted layer can cause runoff, ponding, and plant failure, which increases punch‑list work and warranty calls.
Use a lab report for organic matter, texture, pH, and salinity before importing products. For many landscaped areas, a practical organic target is about 4–6% after mixing, while structural subgrades typically require low organics. Test data also helps justify substitutions when supply changes mid‑project.
Take measured area from plans, choose a mixing depth (often 4–8 in for beds), then convert to cubic yards or cubic meters. As a quick check, 1000 ft² at 6 in equals about 18.5 cubic yards of soil zone. This calculator applies efficiency and waste so orders match real placement conditions.
When specifications call for “blend 10–20% compost,” the volume fraction is straightforward. Example: 1.00 m³ of treated soil at 15% requires 0.15 m³ of amendment before loss factors and overage. This approach fits uniform soils and consistent installation methods.
If you know existing soil organic content and the amendment’s organic content, the calculator estimates the blend fraction to reach a target. It limits extreme values to avoid unrealistic mixes that can shrink, settle, or hold excess moisture. Use it when you have test data and want a repeatable blend.
Bulk density converts volume to tonnes or pounds for trucking and staging. Wet compost can be substantially heavier than dry product, so include density from supplier tickets when possible, especially where crane picks, rooftop planters, or limited access apply.
For small scopes, bag count helps crews avoid underbuying. For large scopes, unit pricing per cubic yard or cubic meter supports bid takeoffs. Add 5–15% waste when stockpiling, wheelbarrowing, or placing on windy days. Compare delivered tickets to takeoff quantities weekly for control.
Confirm mixing depth with a probe, keep amendments out of engineered fills, and avoid burying sod in heavy organic layers. Water after mixing to settle voids, then regrade to finish elevations before planting or seeding. Limit equipment traffic afterward to prevent re‑compaction.
1) What depth should I use for landscape beds?
Many beds are mixed 4–8 inches depending on root zone and irrigation. Use the depth stated in the landscape specification when available, and avoid disturbing structural subgrades.
2) What waste percentage is reasonable?
Use 5–10% for machine-placed material with good access. Use 10–15% for hand spreading, long wheelbarrow runs, or irregular bed edges where trimming and spillage are common.
3) Can I add compost to all site soils?
No. Keep organics out of engineered fills, road bases, and bearing subgrades unless the geotechnical report permits it. Organics can decompose, reduce strength, and contribute to settlement.
4) How do I pick bulk density?
Ask suppliers for typical delivered bulk density or use weigh tickets. Moist product is heavier. If you only have volume pricing, density mainly helps planning equipment limits and trucking loads.
5) What is placement efficiency?
Efficiency accounts for losses during handling, spreading, and mixing. A value near 95% fits controlled placement. Lower it when multiple transfers occur, or when screening and blending create extra loss.
6) Why does the target organic method cap the mix?
Very high amendment fractions can cause shrinkage, excessive moisture retention, and poor compaction. Capping helps keep results within practical construction ranges while still improving soil performance.
7) Should I topdress lawns or fully mix amendments?
Topdressing is lighter and faster but changes soil more slowly. Full mixing improves the root zone quickly but needs more labor and equipment. Match the approach to schedule, irrigation, and the project specification.
Measure twice, amend once, and build healthier ground always.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.