Fertilizer Calculator
Pounds of fertiliser for a target nitrogen rate and NPK.
Enter your values
ⓘ Live results
Results
- Fertiliser needed
- 20.83 lb
- Rate per 1,000 sq ft
- 4.17 lb
- Bags to buy
- 1
- Cost
- $35.00
- Actual N applied
- 5 lb total
Working
- 11 / 0.24 = 4.17 lb per 1000 ft2 x 5
Quick answer
Product needed = target N per 1,000 sq ft divided by the nitrogen percentage, multiplied by the area in thousands of square feet.
lb product = (target N / (N% / 100)) x area/1000
How to use the Fertilizer Calculator
- 1Read the first NPK number on the bag - that is the nitrogen percentage.
- 2Choose a target rate: 0.5 to 1 lb N per 1,000 sq ft per application is typical for lawns.
- 3Spread half in one direction and half at right angles for even coverage.
Worked example
Using the values the calculator loads with:
Inputs
- Area5000 sq ft
- Target nitrogen1 lb N/1000 sq ft
- Nitrogen % (first NPK number)24 %
- Bag size40 lb
- Cost per bag35 $
Results
- Fertiliser needed20.83 lb
- Rate per 1,000 sq ft4.17 lb
- Bags to buy1
- Cost$35.00
- Actual N applied5 lb total
- 1 / 0.24 = 4.17 lb per 1000 ft2 x 5
Frequently asked questions
How much nitrogen per year does a lawn need?
Most cool-season lawns want 2 to 4 lb of nitrogen per 1,000 sq ft per year, split across 3 to 5 applications.
What if I apply too much?
You risk burning the grass and leaching nitrogen into groundwater. Slow-release products are far more forgiving at higher rates.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.