Fertilizer Rate Calculator

The recommendation is written in pounds of nitrogen per 1,000 sq ft. The bag is sold as a percentage analysis on an arbitrary weight. This is the arithmetic that joins the two: enter the analysis and the area, and get pounds of product, bags to buy and the cost per pound of nitrogen you are actually paying.

Lawn area (sq ft)

Turf only. Take out the house, drive, beds and patio — most lawns are a third smaller than the lot.

Bag weight (lb)

Optional — gives you bags to buy and the area one bag actually covers.

Bag analysis (the three numbers on the front)

N — nitrogen %

P — phosphate %

K — potash %

A 21-7-14 bag is 21% nitrogen, 7% phosphate and 14% potash by weight. Phosphate and potash are optional here — nitrogen sets the rate.

Target nitrogen (lb N per 1,000 sq ft)

Or type a rate

0.5 is a maintenance feed; 1.0 is a full autumn feed.

Slow-release N (%)

From the guaranteed analysis panel: coated, sulphur-coated or water-insoluble nitrogen.

Bag price ($)

Optional — turns two different bags into one comparable number.