Free tool from LawnzoLawn fertilizer calculator
Enter the three numbers on the bag, your lawn size and the rate of nitrogen you want. You get the pounds of product per 1,000 sq ft, the total, and how many bags to buy.
Spread per 1,000 sq ft
4.17 lb
20.8 lb for the whole lawn (5,000 sq ft).
- Bags to buy
- 1 (you use 42% of it)
- Nitrogen applied
- 5 lb
- Phosphate (P₂O₅) applied
- 0 lb
- Potash (K₂O) applied
- 2.08 lb
Check the label: its rate and spreader setting come first. Split the total across two passes at right angles for even cover.
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Lawn care calendar by state
- CaliforniaWarm-season lawns are fed from April to September, and tall fescue in spring and fall.
- FloridaFertilize only during the growing season, and finish by late September in the north.
- GeorgiaFeed warm-season grasses from May through August, and tall fescue in February-March and October-November.
- IllinoisFertilize and seed Illinois lawns in late summer, with a lighter feeding in spring.
- MichiganFall is the best time to seed a Michigan lawn, and spring crabgrass control runs by soil temperature, not the calendar.
- New JerseySeed from mid-August to early October, and fertilize only between March 1 and November 15.
- New YorkFeed in September, seed from mid-August through September, and stop by December 1.
- North CarolinaSeed cool-season grass from mid-August to October 1, and warm-season grass from March 1 to July 1.
- OhioFertilize Ohio lawns in April and May and again in September and October.
- PennsylvaniaSeed in late summer to early fall, and feed in spring and again in late summer.
- TexasFeed once the grass is growing, and make the last nitrogen application 4 to 6 weeks before the first frost.
How it works
Lawn recommendations are given in pounds of nitrogen (N) per 1,000 square feet, but you spread product, not nitrogen. The first number on the bag is the percentage of nitrogen by weight, so you divide the rate you want by that percentage.
Example from Iowa State University Extension: to apply 1 lb of N per 1,000 sq ft with a 32-0-4 fertilizer, spread 1 ÷ 0.32 = 3.125 lb of product per 1,000 sq ft. On a 5,625 sq ft lawn that is 3.125 × 5,625 ÷ 1,000 = 17.58 lb.
The same product also carries phosphate (P₂O₅) and potash (K₂O) in the proportion of its second and third numbers; the tool shows how much of each you apply.
Product per 1,000 sq ft = N rate ÷ (N% ÷ 100). Total = product per 1,000 sq ft × lawn area ÷ 1,000.
Good to know
- The right nitrogen rate depends on your grass, your region and the season. A soil test or your state extension office gives the best number.
- Read the bag: its label rate and spreader settings come first, and some states limit phosphorus on lawns.
- Keep fertilizer off driveways and sidewalks, and sweep it back onto the grass.
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<p style="margin:4px 0 0;font-size:14px"><a href="https://lucernel.com/tools/lawn-fertilizer-calculator">Lawn fertilizer calculator by Lawnzo</a></p>Frequently asked questions
How much fertilizer do I need for 1,000 square feet?
Divide the pounds of nitrogen you want by the nitrogen percentage on the bag. For 1 lb of N with a 24-0-10 product: 1 ÷ 0.24 = 4.17 lb of product per 1,000 sq ft.
What do the three numbers on a fertilizer bag mean?
Nitrogen, phosphate (P₂O₅) and potash (K₂O), each as a percentage of the bag weight. A 50 lb bag of 24-0-10 holds 12 lb of nitrogen.
How do I measure my lawn?
Split it into rectangles, multiply length by width for each one, and add them up. Leave out the house, driveway and flower beds.
Sources
- Iowa State University Extension: How to calculate fertilizer rates for the lawn
- University of Missouri Extension: Calculating fertilizer rates
Checked on September 26, 2026.
For the rest, there is Lawnzo
Lawnzo tells you when, not only how much.
Lawnzo builds a season plan for each lawn: when to fertilize, mow, seed and water, checked against the forecast, with a journal of what you did.
- Seasonal plans for your grass type
- Weather checks that keep, delay or skip a task
- A journal of products, quantities and photos
Noted. Every tap tells us how many people want Lawnzo on Android.
See LawnzoGuides about Lawnzo
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