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Home & Garden
Fertilizer Calculator
Find how much fertilizer to apply from area, N rate and N-P-K.
Fertilizer needed
—
Pounds of product.
| Nitrogen needed | — |
|---|---|
| Area | — |
| N rate | — |
| %N | — |
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Enter your figures above to see the step-by-step working.
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How the Fertilizer Calculator Works
Fertilizer is applied by pounds of actual nitrogen per 1,000 square feet, but the bag is only part nitrogen — the first number in the N-P-K label is the percent. First find the nitrogen you need: area divided by 1,000, times the rate. Then divide by the nitrogen fraction to get pounds of product. To put 1 lb of N per 1,000 sq ft on a 5,000 sq ft lawn using a 25-0-4 fertilizer, you need 5 lb of N, which is 20 lb of product.
Most lawns want about 1 lb of nitrogen per 1,000 sq ft per feeding. Slow-release formulas can go a bit higher; never exceed the bag’s label rate, which risks burning the grass and runoff.
product = (area ÷ 1000 × N rate) ÷ (%N ÷ 100)
Frequently Asked Questions
How much fertilizer do I need?
Work out the nitrogen your area needs (area ÷ 1000 × rate), then divide by the nitrogen percent on the bag to get pounds of product.
What does the N-P-K number mean?
It’s the percent by weight of nitrogen, phosphorus and potassium. A 25-0-4 bag is 25% nitrogen, so 100 lb of it contains 25 lb of N.
How much nitrogen per 1,000 square feet?
About 1 lb of actual nitrogen per 1,000 sq ft per application is a common target; follow the product label and your local guidance.
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