About this calculator
Turn a target nitrogen rate into pounds of product from its N-P-K analysis.
How it’s calculated
Product (lb) = area ÷ 1,000 × target N ÷ (N% ÷ 100). A 29-0-4 product at 1 lb N needs 3.45 lb per 1,000 sq ft.
Worked example
With these inputs:
- Area shape
- Rectangle
- Length
- 100 ft
- Width
- 50 ft
- Nitrogen % (first number of N-P-K)
- 29
- Target lb of N per 1,000 sq ft
- 1
- Bag size
- 15 lb
the result is:
- Product needed
- 17.2 lb
- Bags
- 2 × 15 lb
Tips from the trade
- Calibrate the spreader on a driveway first.
- Apply in two passes at right angles to avoid stripes.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and local building codes before ordering.