Fertilizer Calculator
Calculate how many pounds of granular lawn fertilizer you need, based on 5 lbs of product per 1,000 sq ft, plus total cost.
How this calculator works
Granular lawn fertilizer is applied by weight per square foot of turf. This calculator uses a coverage rate of 200 square feet per pound of product, corresponding to roughly 5 lbs of product per 1,000 square feet — a common general-purpose lawn rate.
Formula: Fertilizer (lbs) = Lawn area (sq ft) ÷ 200 sq ft per lb.
Worked example
A 50 ft × 20 ft lawn area (1,000 sq ft):
- Fertilizer needed: 1,000 ÷ 200 = 5.00 lbs
- At $0.90/lb, that’s $4.50.
Coverage reference
| Lawn area | Fertilizer needed |
|---|---|
| 25 × 10 ft | 1.25 lbs |
| 50 × 20 ft | 5.00 lbs |
| 100 × 40 ft | 20.00 lbs |
How to measure your lawn
Measure the length and width of your lawn in feet and multiply for total square footage, combining separate lawn sections into one total unless you’re using different fertilizer blends on each. Cross-check this calculator’s estimate against your specific bag’s printed application rate before setting your spreader, since N-P-K formulations vary the actual per-square-foot dose.
Frequently asked questions
How do I read the N-P-K numbers on a fertilizer bag?
The three numbers are the percentage by weight of nitrogen, phosphorus, and potassium, in that order — a 20-5-10 bag is 20% nitrogen, 5% phosphorus, 10% potassium. This calculator estimates whole product weight; the actual nutrient amount you're applying depends on which N-P-K blend you buy.
How much fertilizer does an average lawn need?
This calculator uses a general rate of about 5 lbs of granular product per 1,000 square feet, or 200 square feet of coverage per pound. Actual rates vary by the specific fertilizer's N-P-K formulation and your grass type, so always check the application-rate table printed on the bag.
When is the best time of year to fertilize a lawn?
For cool-season grasses, early fall and again in late spring are the two most impactful windows, since fall feeding builds root reserves before winter. Warm-season grasses generally do better fertilized through late spring and summer during their active growth period.
What happens if I apply too much fertilizer?
Overapplying granular fertilizer can chemically burn grass blades, leaving yellow or brown streaks where the spreader overlapped, and excess nitrogen that isn't absorbed can run off into storm drains and waterways. Always follow the bag's stated rate rather than assuming more is better.
Slow-release or quick-release fertilizer — what's the difference?
Quick-release fertilizer feeds the lawn fast but for a shorter window and carries a higher burn risk if overapplied, while slow-release (often coated) granules break down gradually over weeks, giving steadier growth with less risk of scorching. Slow-release is generally the safer default for most homeowners.
Estimates only. Verify quantities with your supplier before purchasing.