Fertilizer calculator

How it works

product per 1,000 sq ft = nitrogen to apply / (first number / 100)
product for the lawn  = product per 1,000 sq ft x lawn area / 1,000
one bag covers        = bag size / product per 1,000 sq ft x 1,000

The three numbers on a bag are the percent of nitrogen, phosphate and potash by weight. A 50 pound bag of 24-0-6 holds 12 pounds of nitrogen. Lawn feeding is worked out from the nitrogen, usually 0.5 to 1 pound of it per 1,000 square feet each time.

Keep each feeding to 1 pound of nitrogen per 1,000 square feet or less, and to about half that with quick-release nitrogen in hot weather. Several states limit phosphate on established lawns unless a soil test calls for it, so check before you use a bag with a middle number above zero.

Using the number with a spreader

The bag lists spreader settings for its own rate. To check a spreader, weigh what you load, spread a measured area and weigh what is left; the difference should match the pounds per 1,000 square feet above.

Questions

What do the three numbers on a fertilizer bag mean?

The percent by weight of nitrogen, phosphate and potash, in that order. 24-0-6 is 24% nitrogen, no phosphate and 6% potash.

How much nitrogen should a lawn get at once?

Usually 0.5 to 1 pound per 1,000 square feet a feeding, and no more than 1 pound. Use the lower figure for quick-release products in hot weather.

How many square feet does a bag cover?

Divide the bag weight by the pounds of product per 1,000 square feet and multiply by 1,000. A 50 pound bag of 24-0-6 at 1 pound of nitrogen covers about 12,000 square feet.

Can I use a fertilizer with phosphate?

Several states restrict phosphate on established lawns unless a soil test shows a need. Check your state's rules before you spread it.

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