Lawn Fertilizer Calculator
Tell us your lawn size, your target nitrogen rate, and the N number on the bag, and we'll do the spreading math for you.
📖 How it works & FAQWhat this calculator figures out
Fertilizer bags are sold by weight, but lawns are fed by nitrogen, the first number in the N-P-K label on the bag. A 26-0-4 bag is 26% nitrogen by weight, so only a fraction of every pound you spread is the nutrient your turf actually wants. This tool converts your target nitrogen rate into the real pounds of product to load in your spreader.
The math is simple and exact: product per 1,000 sq ft equals your desired nitrogen divided by the bag's nitrogen fraction (N% ÷ 100). Multiply by your lawn area over 1,000 and you get the total pounds to apply across the whole yard. Enter a bag weight and we'll also round up to how many bags to buy.
Why the nitrogen rate matters
Most cool- and warm-season grasses are fed at about 0.5 to 1.0 lb of nitrogen per 1,000 sq ft per application. Going heavier can burn the lawn and push soft, disease-prone growth. Matching the label rate keeps color and density up without wasting product or money.
How to use it
- Enter your lawn area in square feet (length × width of the turf).
- Enter your target nitrogen rate, usually 0.5 to 1 lb N per 1,000 sq ft.
- Type the bag's first N number, for example 26 for a 26-0-4.
- Optionally add the bag weight to see how many bags to buy.
- Read the pounds per 1,000 sq ft and the total instantly as you type.
FAQ
- Which bag number is the nitrogen?
- The first of the three N-P-K numbers. In 26-0-4, nitrogen is 26%.
- What rate should I use?
- 1 lb N per 1,000 sq ft is a common maintenance dose; use 0.5 for a gentle feed or on sensitive grass.
- Does this set my spreader number?
- No. It gives total pounds to apply. Use your spreader's chart or a small test pass to hit that amount evenly.
- Are these results exact?
- These are estimates for planning, not professional agronomic advice; always follow the product label and local rules.