Lawn Fertilizer Calculator
Enter your fertilizer label, a target rate from your local guidance, and the lawn area. Calculate product weight, whole bags, cost and leftovers. This tool calculates quantities; it does not choose a safe rate or feeding schedule.
- Free to use
- No sign-up
- Runs in your browser
Lawn fertilizer calculator
Lawn Fertilizer Planner Pack
Optional editable records: three spreadsheets and two Word documents. All five PDFs are free on this site. Includes a nitrogen quantity planner; no custom lawn treatment or subscription.
- Nitrogen planning record
- Blank feeding plan
- Spreader calibration record
- Soil test record
- Lawn care log
Formats: PDF, XLSX, DOCX. Instant download after payment (link valid 72 hours, up to 5 downloads). AI-assisted: AI tools were used to help draft these materials.
$5.00 USD, one-time
- Instant download
- 7-day refund
- Secure checkout by Stripe
7-day money-back guarantee. Full refund within 7 days of purchase, even after you download.
Full refund within 7 days — see the refund policy and license.
Free printables
Single sheets you can print right now, no sign-up. The full pack adds every sheet in one download plus the editable files.
Nitrogen planning record (manual PDF)
Blank feeding plan (manual PDF)
Spreader calibration record (manual PDF)
Soil test record (manual PDF)
Lawn care log (manual PDF)Start with the label and your local guidance
The N-P-K analysis gives nitrogen, phosphate (P₂O₅) and potash (K₂O) percentages by weight. Match the target nutrient and its unit to your guidance. A nutrient rate is different from pounds of product. Do not substitute elemental P or K for phosphate or potash without the appropriate conversion.
Calculation example
| Input or result | Example only |
|---|---|
| Area | 5,001 sq ft |
| Target nitrogen | 0.75 lb N per 1,000 sq ft |
| Product nitrogen | 25% |
| Product quantity | 0.75 / 0.25 × 5,001 / 1,000 = 15.003 lb |
| Bag weight | 15 lb |
| Purchase | 2 bags; apply only the permitted quantity, retain the rest |
How the calculator works
- Product per 1,000 sq ft = target nutrient rate divided by its label fraction.
- Total product = product per 1,000 sq ft multiplied by area / 1,000. One m² is converted using 1 sq ft = 0.09290304 m².
- Bag count rounds the unrounded total up to whole bags. Cost uses your USD price per bag and excludes delivery and tax.
- Leftover product is purchased weight minus the calculated application amount. Quantities display up to six decimal places.
Input limits
Each label percentage must be between 0 and 100. A positive target requires a positive percentage for that nutrient. Rate accepts 0 to 100; area and price accept 0 to 1 billion; bag weight must be positive and at most 1 billion lb. These are software bounds, not recommended application rates. Results beyond numeric precision are rejected.
Five PDFs are free
Use the manual nitrogen planning record, blank feeding plan, spreader calibration record, soil-test record and lawn-care log without paying. The PDFs have no automatic calculations or interactive fields.
What the optional $5 pack adds
Three XLSX files and two DOCX files. The nitrogen planner calculates product and bags across 11 rows. The other two spreadsheets are manual soil and lawn records with units. The feeding plan and calibration record are editable Word documents. The ZIP also contains the five free PDFs and a README: 11 files total.
Keep expectations clear
The workbook uses nitrogen, sq ft and lb; the web calculator additionally supports phosphate, potash and m². No file decides application timing, interprets a soil report or sets a spreader dial. Files do not synchronize. Worksheet totals assume separate purchases, without stock carryover.
Free specialist guidance
University of Minnesota Extension explains lawn nutrients and site-dependent needs. Clemson explains spreader calibration and effective width. Use guidance appropriate to your location and the product label. These free resources may meet your needs without an editable pack.
Frequently asked questions
Does this tell me how much fertilizer my lawn needs?
It converts a target rate you supply into product quantity. Obtain the rate from your product label and appropriate local guidance first.
Why are two bags needed when the displayed amount looks near 15 lb?
Bag count uses the unrounded quantity. For example, 15.003 lb needs two 15 lb bags. Display rounding does not reduce the purchase requirement.
Can I enter square metres?
Yes. Choose m² for the web calculator. The planning workbook uses sq ft and lb only.
What happens if my fertilizer contains zero of the selected nutrient?
A positive target cannot be met; the calculator asks you to choose another product or target. A zero target produces zero product.
Are the PDFs included in the price?
They are also available free. The optional $5 pack adds three editable spreadsheets and two editable Word records.
Are soil results interpreted or schedules recommended?
No. Record your laboratory results and local guidance with their units and sources. No universal feeding months or rates are provided.