Lawn Fertilizer Calculator (NPK and Spreader Rate)
Work out how many pounds of fertilizer to apply to a lawn for the nitrogen rate you want.
Runs in your browser. Your files never leave your device. See how to check
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How to do it
- 1Step 1: Open Lawn Fertilizer Calculator (NPK and Spreader Rate) and add your input
Type your numbers or text, add your file, or pick the options you need. Nothing is uploaded: everything stays in your browser.
- 2Step 2: What Lawn Fertilizer Calculator (NPK and Spreader Rate) does
Work out how many pounds of fertilizer to apply to a lawn for the nitrogen rate you want.
- 3Step 3: Read the result and compare
The result appears at once. Change one value to see how the answer moves, then keep the figure that fits your case.
- 4Step 4: Copy or save it
Copy the result or download it. For an important decision, confirm it with the official source or an adviser.
About this tool
Enter the lawn area, the pounds of nitrogen per 1,000 square feet you want, the nitrogen percentage on the bag and the bag weight. The calculator gives the pounds of product, the rate per 1,000 square feet and the number of bags.
Formula
Pounds of product = area ÷ 1,000 × nitrogen rate ÷ nitrogen fraction. A 24-0-6 bag is 24% nitrogen, so applying 1 lb of nitrogen per 1,000 ft² takes 4.17 lb of product per 1,000 ft².
Rates
A typical application is 0.5 to 1 pound of nitrogen per 1,000 square feet, a total of 2 to 4 pounds over the year for cool-season grasses. Do not apply more than 1 pound of quick-release nitrogen at a time.
Spreader
Set the spreader to the setting printed on the bag for the rate. Calibrate it on a small area first.
Worked example
5,000 ft² of lawn at 1 lb of nitrogen per 1,000 ft² with a 24% nitrogen fertilizer needs 20.8 lb of product, or about 1.4 bags of 15 lb.
Tips for best results
Check every box before you rely on a result, because one wrong digit changes the whole answer. Use the exact figures from your payslip, bill, certificate or contract, and keep a note of the date you calculated. Rates, thresholds and rules change from time to time, so for tax, fees and legal matters treat the output as an estimate and confirm with the official source named on this page. You can run as many scenarios as you like; nothing is saved or sent, and refreshing the page clears the boxes.
Quick facts
- Category: UK & US
- Works in your browser, no sign-up, no upload.
- Your input stays on your device.
- Available in English.
- Content last reviewed:
Frequently asked questions
What do the three numbers mean?
The percentages of nitrogen, phosphorus and potassium.
How often should I fertilize?
2 to 4 times a year for cool-season grass, depending on the type.
Can I put on more?
Too much burns the grass and pollutes runoff.
Do I measure the lawn area carefully?
Yes, the dose depends on it.