What Do the Numbers on Lawn Fertilizer Mean

What do the numbers on lawn fertilizer mean? They mean the percentage by weight of nitrogen, phosphate and potash in the bag, in that order. A bag marked 24 0 6 holds 24 percent nitrogen, 0 percent phosphate and 6 percent potash. Lawns mainly need nitrogen, so the first number sets how much product you spread for each feed.

What do the numbers on lawn fertilizer mean in plain words

The three numbers on a lawn fertilizer bag are a grade, always in the same order. The first number is nitrogen. The second number is phosphate. The third number is potash. Each number is a percentage by weight, not a weight in pounds or kilograms. It means a share of that nutrient in each pound or kilogram of product.

The calculator page states the same definition in short form. N P K means nitrogen, phosphate and potash percentages, and lawns mainly need nitrogen. The University of Massachusetts Amherst fact sheet Understanding a Turf Fertilizer Label calls the three numbers the guaranteed analysis, or grade, with the first number as percent nitrogen, the second as percent phosphate as P2O5, and the third as percent potash as K2O.

Test it with a bag you can lift. A 50 pound bag of 24 0 6 holds 12 pounds of nitrogen, no phosphate, and 3 pounds of potash. The numbers add to 30 percent, so 70 percent is carrier material. That is normal. The numbers are not meant to add to 100 percent.

The first number: nitrogen

Nitrogen is the first number, and for a lawn it is the number that matters most. Nitrogen drives leaf growth and green colour. A lawn short of nitrogen grows slowly and looks pale. That is why lawn advice is given in pounds of nitrogen per 1,000 square feet, not in pounds of product. The product is only the carrier. The nitrogen inside it is the feed.

The calculator page gives a standard amount per feed of around 1 pound of nitrogen per 1,000 square feet, also given as 5 grams per square metre in rounded form. It also gives a cool season annual need of 2 to 4 pounds per 1,000 square feet a year, also given as 10 to 20 grams per square metre in rounded form. Warm season lawns vary by grass type, and the page gives no figure for them. A higher first number means you spread less product per feed.

The second number: phosphate

Phosphate is the second number, listed as phosphate and expressed as P2O5 on labels. Phosphate supports root development. It matters most when a lawn is being established. For an established lawn, phosphate is often already present in the soil in enough amount, so many lawn products carry a low second number or a zero.

A zero in the middle is therefore common. It does not mean the product is faulty. It means the product supplies no phosphate. If the soil already holds enough phosphate, adding more does not help, and it can add to runoff. Follow local rules, because some areas restrict phosphorus or seasonal feeding. The page gives no phosphate rate for lawns, so this blog gives no phosphate amount per feed, per 1,000 square feet, or per year.

The third number: potash

Potash is the third number, listed as potash and expressed as K2O on labels. Potash helps the grass cope with stress, and supports tolerance of wear, heat, cold and drought. It does not drive leaf growth in the way nitrogen does, and it does not build roots in the way phosphate does.

In 24 0 6, the third number is 6, so 6 percent of the product by weight is potash. A 50 pound bag holds 3 pounds of potash. The page gives no potash rate for lawns, so this blog gives no potash amount per feed, per 1,000 square feet, or per year. Do not use the third number to set the spread rate.

Number	Nutrient	What the number means	What it does for a lawn
First	Nitrogen	Percent nitrogen by weight	Drives leaf growth and green colour
Second	Phosphate	Percent phosphate by weight, as P2O5	Supports root development
Third	Potash	Percent potash by weight, as K2O	Helps the grass cope with stress

What 0 means in 24 0 6

A zero in a grade is a clear statement. It means that nutrient is not in the product. In 24 0 6, the zero is in the second place, so the product has 24 percent nitrogen, 0 percent phosphate and 6 percent potash. Readers sometimes treat a zero as a gap to fill, or as a sign that the product is weak. Neither reading follows from the grade alone.

A lawn that already has enough phosphate does not need phosphate in every feed. A product with a zero in the middle can fit that lawn, and it can fit a local rule that restricts phosphorus. If you see a grade with a zero in the first place, the product has no nitrogen, and it cannot supply nitrogen for a feed. Each position belongs to one nutrient only.

Why the first number sets your product rate

The calculator formula is short, and it uses only the first number. Product rate equals nitrogen per feed divided by nitrogen percent. Per feed equals product rate times area. Per year equals per feed times feeds. Bags equal the amount divided by bag weight, rounded up to a whole bag. The second and third numbers do not enter the calculation at all, because lawn feeding is measured in nitrogen.

To reach 1 pound of nitrogen with a 24 percent product, divide 1 by 0.24. The result is 4.17 pounds of product per 1,000 square feet, which the page rounds to roughly 4 pounds. With a 29 percent product, divide 1 by 0.29. The result is 3.45 pounds, which the page rounds to roughly 3.5 pounds. For 20 percent, 1 divided by 0.20 equals 5 pounds. For 16 percent, 1 divided by 0.16 equals 6.25 pounds. Those two results are calculated from the page formula, not stated on the page.

First number, nitrogen percent	Product for 1 pound nitrogen per 1,000 square feet
16	6.25 pounds, calculated from the formula
20	5 pounds, calculated from the formula
24	4.17 pounds, page rounds to roughly 4 pounds
29	3.45 pounds, page rounds to roughly 3.5 pounds

Use the lawn fertilizer calculator to run the same division for your own lawn area and your own first number, rather than copying a product amount from a different grade. The calculator asks for lawn area, nitrogen percent and nitrogen per feed, then gives the fertilizer per feed, the spreader rate and the bags for the year. This blog explains the numbers. The calculator applies them.

How a higher first number changes the amount you spread

As the first number rises, the product amount falls. The difference between 24 percent and 29 percent is only about 0.7 pounds of product per 1,000 square feet for 1 pound of nitrogen, but it grows with lawn size. For a lawn of 5,000 square feet, the difference is about 3.6 pounds of product per feed.

A higher first number also means each pound of product carries more nitrogen, so a spreading error has a larger effect. Spread 1 pound too much with a 24 percent product, and you add 0.24 pounds of nitrogen too much. With a 29 percent product, you add 0.29 pounds too much. Calibrate the spreader to the rate shown by the calculator, as the page instructs, and apply in two directions.

The worked example in 24 0 6, in brief

The calculator page gives one worked example, and the other blogs in this batch give the full guide to it. A 400 square metre lawn fed 4.9 grams of nitrogen per square metre with 24 0 6 needs 8.17 kilograms per feed, and one 10 kilogram bag. Four feeds a year take 32.7 kilograms, which is four bags.

The imperial example is separate. A 5,000 square foot lawn at 1 pound of nitrogen per 1,000 square feet needs 20.8 pounds per feed, and 83.3 pounds a year, which is six 15 pound bags. Those figures work out to 24 percent nitrogen and 4 feeds a year, as a derived reading, not as a statement on the page.

Common mistakes

1. Reading the numbers as pounds in the bag. They are percentages by weight. A grade of 24 0 6 means 24 percent of the bag weight is nitrogen.
2. Adding the three numbers and expecting 100. In 24 0 6 they add to 30. The rest is carrier material.
3. Using the second or third number to set the spread rate. The rate comes from the first number and the nitrogen per feed.
4. Treating a zero as a fault. In 24 0 6 the zero means no phosphate, which can fit an established lawn or an area with a phosphorus restriction.
5. Comparing products by bag weight alone. Two bags can weigh the same and hold very different amounts of nitrogen.
6. Spreading product weight as if it were nitrogen weight. Spreading 1 pound of a 24 percent product gives only 0.24 pounds of nitrogen.
7. Ignoring the overfeeding warning. Excess nitrogen can scorch grass, encourage disease and wash into waterways, as the page FAQ states.
8. Copying a spread amount from a different grade. A rate that is right for 24 percent is wrong for 29 percent.

Frequently asked questions

Q: What do the numbers on lawn fertilizer mean?
A: They mean the percentage by weight of nitrogen, phosphate and potash in the bag, in that order. A bag marked 24 0 6 holds 24 percent nitrogen, 0 percent phosphate and 6 percent potash.

Q: Which number on lawn fertilizer is the most important for a lawn?
A: The first number, nitrogen, because lawns mainly need nitrogen and the calculator sets the product rate from nitrogen per feed divided by nitrogen percent.

Q: What does 0 mean in 24 0 6 lawn fertilizer?
A: The 0 means the product has 0 percent phosphate. It supplies nitrogen and potash, and no phosphate.

Q: How much product do I need for 1 pound of nitrogen per 1,000 square feet?
A: Divide 1 pound by the first number as a decimal. For 24 percent, 1 divided by 0.24 equals 4.17 pounds, which the page rounds to roughly 4 pounds. For 29 percent, 1 divided by 0.29 equals 3.45 pounds, which the page rounds to roughly 3.5 pounds.

Q: Why does a higher first number mean less product per feed?
A: A higher first number means the product is more concentrated in nitrogen. For 1 pound of nitrogen, a 16 percent product needs 6.25 pounds, a 20 percent product needs 5 pounds, a 24 percent product needs 4.17 pounds, and a 29 percent product needs 3.45 pounds.

Q: Can I put down too much lawn fertilizer?
A: Yes. Excess nitrogen can scorch grass, encourage disease and wash into waterways. Do not fertilize a dormant or drought stressed lawn, keep fertilizer off paths and drives, sweep up spills, and follow local rules.