Lawn Fertilizer Calculator: How Much to Apply
Work out how much fertilizer to spread. Enter your lawn area, the nitrogen rate you want, and the first number on the bag, and get the product weight to apply.
How to calculate lawn fertilizer
- Enter the lawn area in square feet.
- Set the target nitrogen rate, usually 1 lb of N per 1000 sq ft.
- Enter the nitrogen percent from the bag and read the pounds to apply.
Examples
5000 sq ft at 1 lb N with a 26-0-3 product
Area 5000, rate 1, nitrogen 26%
5 lb of nitrogen, about 19.23 lb of product
Frequently asked questions
How much fertilizer do I need per 1000 square feet?
A common target is 1 lb of actual nitrogen per 1000 sq ft per feeding. The bag weight needed depends on its nitrogen percent: at 26% nitrogen you apply about 3.85 lb of product per 1000 sq ft to deliver 1 lb of nitrogen.
What do the numbers on a fertilizer bag mean?
The three numbers are the NPK analysis: percent nitrogen, phosphorus and potassium by weight. A 26-0-3 bag is 26% nitrogen, which is the figure this calculator uses to size the application.
How do I find pounds of product from pounds of nitrogen?
Divide the nitrogen you want by the nitrogen fraction. For 1 lb of nitrogen from a 20% product, that is 1 divided by 0.20, which is 5 lb of product.
Can I apply too much nitrogen?
Yes. Over applying can burn the lawn and pollute runoff. Most lawns do best at no more than about 1 lb of nitrogen per 1000 sq ft per application, with a few weeks between feedings.
Does this work for any fertilizer?
It works for any product where you know the nitrogen percent, including granular and slow release lawn fertilizers. Enter that percent and the calculator handles the rest.
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