Formula Used
Area: rectangle = length × width; circle = π × radius²; triangle = base × height ÷ 2.
Soil volume: treatment area × incorporation depth.
Mass-based need: application rate × treatment area.
Volume-based need: volume rate × treatment area.
Moisture correction: dry mass = wet mass × (1 − moisture fraction).
Carbon: dry biochar × carbon fraction × stable fraction.
CO₂ equivalent: stable carbon × 3.667.
Biochar needs depend on area, depth, rate, and density. Moisture changes purchased mass but not dry carbon content. Use measured supplier data whenever accurate project estimates matter.
How to Use
- Choose the site type and enter its dimensions.
- Select the application method matching your recommendation.
- Enter measured density, moisture, and carbon properties.
- Add bag, delivery, charging, and cost details.
- Calculate, review warnings, and export the summary.
Choose the site type and enter every available dimension. Select an application method matching your agronomic recommendation. Review warnings before purchasing or applying any soil amendment.
Worked Example Data
| Input | Example value | Purpose |
|---|---|---|
| Garden size | 10 m × 5 m | Creates 50 m² treatment area |
| Incorporation depth | 15 cm | Creates 7.5 m³ soil volume |
| Application rate | 1.5 kg/m² | Creates 75 kg dry biochar |
| Dry bulk density | 250 kg/m³ | Converts mass into volume |
| Moisture content | 15% | Estimates wet delivered mass |
| Bag size | 10 kg | Rounds purchasing quantities upward |
| Bag price | £18 | Calculates estimated material cost |
Costs combine materials, delivery, labour, equipment, and amendments. Tax and contingency are calculated from the entered percentages. Confirm supplier prices before approving any final project budget.
Important Limitations
- Application recommendations vary across soils, crops, and climates.
- Supplier density and moisture values can change between batches.
- Carbon permanence depends on production quality and field conditions.
- Charging quantities are planning estimates, not mandatory prescriptions.
- Consult local agronomic guidance before high-rate field applications.
Carbon estimates use dry mass, carbon fraction, and stability. The factor 3.667 converts carbon mass into carbon dioxide. Actual permanence varies with production quality and field conditions.
Frequently Asked Questions
What bulk density should I enter?
Use the supplier's measured bulk density for your batch. Dry and wet density values produce different mass conversions. Verify the density basis before calculating any purchase quantity.
Should application rates use dry or wet mass?
Most technical recommendations use dry biochar mass. Purchased bags may show as-received wet mass instead. Match the selected mass basis with your source recommendation.
How does moisture correction work?
Moisture adds transported weight without adding dry carbon. The calculator converts between wet and dry quantities. Accurate moisture data improves bags, loads, and cost estimates.
What does final blend percentage mean?
It measures biochar within the combined soil-biochar volume. Soil addition percentage uses only existing soil volume. Select the definition used by your agronomic recommendation.
Why are bags rounded upward?
Suppliers usually sell complete bags rather than fractions. Rounding prevents purchasing less than the calculated requirement. Waste allowance adds further protection against handling losses onsite.
Can I calculate raised beds and pots?
Yes, separate geometry handles beds, pots, and holes. Each mode calculates soil volume from entered dimensions. Per-unit rates also support plants, containers, and planting holes.
What is biochar charging?
Charging mixes biochar with nutrients before soil application. Compost, water, and fertiliser estimates support project planning. Follow product guidance and local agronomic advice when charging.
How is carbon dioxide equivalent estimated?
Stable carbon mass is multiplied by 3.667. This converts carbon into an equivalent carbon dioxide mass. The result remains an estimate rather than verified credits.
Can I compare multiple application rates?
Yes, enter low, typical, and high values. The comparison recalculates mass and volume for each rate. Use scenarios to compare recommendations before selecting purchase quantities.
Why does the calculator show warnings?
Warnings identify unusually high rates or unusual properties. They do not automatically prove an input is wrong. Review them before finalising any field application decision.
Can I export and share calculations?
Yes, results support copy, CSV, PDF, sharing, and printing. The merged summary includes inputs, outputs, costs, and warnings. Keep exported records with supplier specifications and field notes.