Choose your fertilizer type and target nutrient rate. We convert analyses into practical application amounts. Download tables, share results, and grow stronger plants daily.
| Area | Target | Rate | Material | Availability | Efficiency | Estimated fertilizer |
|---|---|---|---|---|---|---|
| 100 m² | N | 5 g/m² | Compost (1-0.5-1) | 20% | 90% | 138.889 kg |
| 1,000 ft² | N | 0.5 lb/1000 ft² | Blood meal (12-0-0) | 70% | 85% | 2.243 kg |
| 0.25 acre | P₂O₅ | 10 lb/acre | Bone meal (3-15-0) | 60% | 90% | 5.605 kg |
| 50 m² | K₂O | 4 g/m² | Kelp meal (1-0.1-2) | 50% | 90% | 44.444 kg |
Examples use typical analyses and release estimates. Always confirm labels and local guidance.
This calculator converts a nutrient target into a fertilizer amount using the material’s analysis, an expected first-season release (availability), and an application efficiency factor.
Volume estimate uses: Volume(L) = Fertilizer required(kg) ÷ Bulk density(kg/L).
Start with a soil test and a realistic crop goal. Many home gardens aim for modest seasonal additions, such as 3–8 g of nitrogen per m2 for leafy beds, and lower nitrogen for fruiting crops once established. Use your area and a single nutrient target so the calculator can translate your plan into a measurable amount.
Organic materials are commonly labeled with N–P2O5–K2O percentages. A 3–15–0 product means 3% nitrogen and 15% phosphate equivalent by weight. Low-analysis materials like compost (often near 1% nitrogen) require larger application masses, which is normal and can improve soil structure when applied responsibly.
Unlike soluble fertilizers, many organic nutrients release gradually. “First-season availability” estimates the portion that becomes plant-available during the target period. For example, a 20% availability setting means only one-fifth of the listed nutrient is expected to supply this season, with the remainder mineralizing later. Adjust availability upward for finely processed meals and warm, active soils.
Application efficiency accounts for losses from handling, runoff, wind drift, or uneven spreading. A 90% efficiency assumption is reasonable when you incorporate material lightly and irrigate afterward. For broadcast application, calibrate your spreader by weighing a small test load, covering a known area, and comparing actual coverage to the plan. Consistent distribution protects seedlings and reduces patchy growth.
Bulk density converts kilograms into practical volume for buckets and carts. Compost-like materials often range around 0.4–0.8 kg/L, while meals are denser. Use the cost fields to compare options per season rather than per bag. Avoid over-application of phosphorus-rich amendments near waterways, and recheck soil tests annually to keep nutrients balanced.
Compost typically has low nutrient percentages. A 1% nitrogen material contains 0.01 kg N per kg, so meeting a nutrient target naturally needs more kilograms. The benefit is added organic matter and improved soil tilth.
Pick the nutrient you are specifically correcting from a soil test. Nitrogen supports vegetative growth, while P2O5 and K2O relate to rooting, flowering, and stress tolerance. Avoid “chasing” all three without evidence.
Use a conservative estimate if you are unsure. Coarser composts may release slowly, while fine meals release faster. Temperature, moisture, and microbial activity matter. When in doubt, start lower and observe plant response.
It is a planning estimate. Moisture content and particle size change bulk density. If precision is needed, fill a known-volume container, weigh it, then update the bulk density field for your exact material.
Yes, but use container surface area or media volume thoughtfully. Many potting mixes have different nutrient dynamics than mineral soils. Start with smaller rates, mix thoroughly, and monitor salts and moisture to avoid root stress.
Efficiency represents how much of the planned nutrient actually reaches the root zone. Lower efficiency increases required fertilizer to compensate for losses. Improving placement and incorporation often saves material and reduces runoff risk.
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.