Fertilizer Calculator
How many bags to hit a nitrogen rate — not an agronomy prescription. Click any i for detail.
Lawn and bag
Area (sq ft)
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Area
Turf you will fertilize. |
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N rate (lb N / 1,000 sq ft)
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N rate
Pounds of actual nitrogen per 1,000 sq ft this application. Many cool-season programs use ~0.75–1 lb N per pass. |
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Bag nitrogen (%)
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N %
First number in N-P-K. A 30-0-4 bag is 30% N by weight. |
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Bag weight (lb)
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Bag
Net weight on the bag. |
How to use this calculator
- Enter lawn area.
- Set the lb N per 1,000 you want this pass.
- Enter the bag’s N% and weight.
- Ceil bags; don’t dump leftovers just to empty a bag on a small lawn.
Results explained
Need (lb N) = (sq ft ÷ 1,000) × N rate. Product lb = need ÷ (N% / 100). Bags = product lb ÷ bag weight.
Quick reference: N math
A 50 lb 30-0-4 bag holds 15 lb of actual nitrogen.
| Item | Detail |
|---|---|
| 50 lb @ 30% N | 15 lb N / bag |
| 1 lb N / 1,000 on 5,000 sq ft | 5 lb N needed |
| Those 5 lb N | ⅓ of that 50 lb bag |
| Grass seed pounds | Grass seed calculator |
Phosphorus and potassium are not sized here — only nitrogen.
How the estimate is built
bags = ((area/1000)×N_rate) ÷ (bag_lb × N%/100).
Example scenario
5,000 sq ft, 1 lb N/1,000, 30% N, 50 lb bag → 5 lb N needed → 0.33 bags (ceil 1).
FAQ
Soil test first?
Yes if you can. This page only does bag arithmetic.
Slow-release?
Same N math; timing is separate.
Liquid fertilizer?
Convert the label to lb N / 1,000 and use that rate.