Fertilizer calculator
Fertilizer application rate calculator
Convert fertilizer application rates between lb/acre and kg/ha, then estimate the total product needed for a field, plot or lawn area.
Calculate total product
Rate conversion formula
The unit conversion is based on exact NIST acre and pound definitions.
Common NPK formulas
| Formula | N-P-K % | Typical use | Crop/context | Indicative rate context |
|---|---|---|---|---|
| 10-10-10 | 10-10-10 | Balanced complete fertilizer | Vegetable gardens, tomatoes, potatoes, small fruits | 1.5–3 lb/100 sq ft; 20–35 lb/1,000 sq ft seasonal |
| 12-12-12 | 12-12-12 | Balanced complete fertilizer | Garden and general purpose use | 1–2 lb/100 sq ft; sometimes 2–3 |
| 13-13-13 | 13-13-13 | Concentrated complete fertilizer | Gardens, strawberries, roses, food plot/pasture with soil test | 2–3 lb/100 sq ft; strawberries 3–4 lb per 8×30 ft bed |
| 16-4-8 | 16-4-8 | Higher N and K, lower P | Lawns, ornamentals, landscape | 4.7–6.25 lb/1,000 sq ft for 0.75–1.0 lb N |
| 19-19-19 | 19-19-19 | Concentrated complete fertilizer | Intensive vegetables, high tunnels, low-P soils | 0.5–1.0 lb/100 sq ft; about 200 lb/acre in context |
| 20-20-20 | 20-20-20 | Soluble complete fertilizer | Annuals, flowers, containers, light fertigation | 0.5–1.0 lb/100 sq ft indicative |
| 21-0-0 | 21-0-0 | Ammonium sulfate; N + sulfur | Crops needing N and S; alkaline soils; acid-loving plants | 4.8 lb/1,000 sq ft for 1 lb N |
| 34-0-0 | 34-0-0 | Ammonium nitrate; nitrogen only | Agronomic crops, pasture, side-dress N | 2.9–3.0 lb/1,000 sq ft for 1 lb N |
| 46-0-0 | 46-0-0 | Urea; concentrated nitrogen | Corn, cereals, lawn | 2.2 lb/1,000 sq ft for 1 lb N |
| 18-46-0 | 18-46-0 | DAP; phosphorus + nitrogen | Starter fertilizer, corn, cereals, P correction | 2.2 lb product per 1 lb P₂O₅; lower near-seed limits |
Open the dedicated NPK fertilizer application rate table for a cleaner reference-table view.
Specific fertilizer products
| Product | Type | Typical rate | Unit | Use / note |
|---|---|---|---|---|
| Urea | Synthetic | 2.2 | lb/1,000 sq ft per 1 lb N | 46-0-0 concentrated nitrogen |
| DAP | Synthetic | 2.2 | lb product/lb P₂O₅ | 18-46-0 starter or P correction |
| Milorganite | Organic | 32 | lb/2,500 sq ft established lawn | 6-4-0; 85% N water-insoluble; 2.5% iron |
| Blood meal | Organic | 1–2 | lb/100 sq ft | Fast organic N for gardens, flowers, shrubs |
| Bone meal | Organic | 10 | lb/100 sq ft | P + calcium for bulbs, beds, roots, flowering |
| Gypsum | Amendment | 1 | lb/100 sq ft | Calcium + sulfur; does not raise pH |
| Lime | Amendment | 25–50 | lb/1,000 sq ft | Correcting acidic soil pH |
| Ammonium sulfate | Synthetic | 4.8 | lb/1,000 sq ft per 1 lb N | 21-0-0-24S; acidifying effect |
| Chicken manure | Organic | 3–4 new bed; 0.25–1 existing bed | inches applied | Use mature/composted material and follow food safety guidance |
| Cow manure | Organic | 3–4 new bed; 0.25–1 existing bed | inches applied | Slower amendment than poultry manure |
Open the specific fertilizer rates table for product-specific context such as urea, DAP, Milorganite, lime, gypsum and manure.
FAQ
How do I convert lb/acre to kg/ha?
Multiply lb/acre by 1.120851. The calculator uses exact pound and acre-to-hectare constants.
Is an NPK table a fertilizer recommendation?
No. NPK percentages and common rate ranges are context. Actual fertilizer decisions should use a soil test, crop target and local guidance.
What does 46-0-0 mean?
A 46-0-0 fertilizer contains 46% nitrogen, 0% phosphate and 0% potash by guaranteed analysis convention.