Fertilizer Calculator

Want to know where these numbers came from?

The N-P-K ratio on a fertilizer bag looks like this. | Photo Credit: Janice Milanovich, Illinois-Indiana Sea Grant

If you’d like to calculate the total pounds of fertilizer needed yourself, you can. For example, let’s figure out how much fertilizer you need to apply a fertilizer with a N-P-K ratio of 22-0-15 at 1 pound (lb) of Nitrogen (N) per 1,000 square foot (ft²) to a 5,000 ft ² lawn.

• First, to calculate the total fertilizer need (in lbs. per 1, 000 ft²), divide the desired rate (lbs. N per 1, 000 ft²) by the % nutrient.
• 1 /1,000 ft² divided by .22 = 4.545, round to 4.5 lbs./1,000 ft²
• Next, using that information, you can calculate the pounds of fertilizer needed for your sized lawn. Multiply the total fertilizer need from the first calculation (lbs./1, 000 ft²) by the size of the area to be treated (ft²).
• 4.5 lbs./1,000 ft² multiplied by 5,000 ft² = 22.5 lbs
• Therefore, 22.5 lbs. of fertilizer are needed for a 5,000 ft²