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Calculate the perfect amount of fertilizer for your lawn. Get personalized NPK recommendations based on your grass type, lawn size, and seasonal needs.
Methodology by James Thornton, Lawn Equipment & Maintenance Expert | 20 Years. Reviewed March 15, 2026. Based on university extension service guidelines.
Note: These recommendations are estimates based on general guidelines. For best results, consider a soil test to determine your lawn's specific nutrient needs. Always follow fertilizer label instructions and local regulations.
The three numbers on every fertilizer bag are the percentages of nitrogen (N), phosphorus (Pâ‚‚Oâ‚…), and potassium (Kâ‚‚O) by weight.
Example: a 50 lb bag of 10-10-10 Balanced Fertilizer contains 10% nitrogen, 10% phosphorus, and 10% potassium by weight. That works out to 5 lbs of actual nitrogen per bag.
Nitrogen drives green color and leaf growth. Phosphorus supports root development — important for new lawns and starter fertilizers. Potassium builds stress, drought, and winter hardiness — which is why winterizer blends lean high on K.
If you want a deeper explanation of how the label math works, the guide at /blog/how-to-read-fertilizer-numbers walks through reading and comparing product labels.
Standard target: 1 lb of nitrogen per 1,000 sq ft per application. The formula is (1 ÷ %N) × (lawn area ÷ 1,000).
For a 5,000 sq ft lawn targeting 1 lb N per 1,000 sq ft, here's how three common products compare:
| Fertilizer | Rate formula | Product needed | Bags |
|---|---|---|---|
| 10-10-10 Balanced Fertilizer | (1 ÷ 0.10) × 5 | 50 lbs | 1 × 50 lb |
| 32-0-4 High Nitrogen | (1 ÷ 0.32) × 5 | 16 lbs | 1 × 50 lb |
| 18-24-12 Starter Fertilizer | (1 ÷ 0.18) × 5 | 28 lbs | 1 × 42 lb |
Note how a higher-nitrogen product requires far less material to deliver the same 1 lb N per 1,000 sq ft.
Five product categories. Pick the one that matches your goal, season, and grass type.
| Category | Example NPK | When to use |
|---|---|---|
| Balanced | 10-10-10 | All-purpose balanced fertilizer suitable for most lawns. Provides equal amounts of nitrogen, phosphorus, and potassium. |
| High Nitrogen | 32-0-4 | High nitrogen formula for promoting lush green growth. Ideal for established lawns needing color enhancement. |
| Starter | 18-24-12 | High phosphorus starter fertilizer perfect for new lawns, overseeding, and root development. |
| Organic | 6-2-0 | Natural organic fertilizer made from composted materials. Safe for pets and children, improves soil health. |
| Specialty (slow-release) | 15-5-10 | Slow-release nitrogen formula provides steady feeding over 8-12 weeks. Reduces burning risk and extends feeding. |
| Specialty (winterizer) | 22-0-8 | Fall fertilizer with high nitrogen and potassium for winter hardiness and spring green-up. |
If you're picking a single yearly timing to add, the guide at /blog/10-10-10-fertilizer-when-how-to-apply covers the most common scenarios for balanced fertilizer.
Price anchors from the app's product catalog. Useful for sanity-checking a store shelf or Amazon listing.
| Product | Price range | Bag size | Category |
|---|---|---|---|
| 10-10-10 Balanced Fertilizer | $1.20-$1.50/lb | 50 lb bags | balanced |
| 32-0-4 High Nitrogen | $1.30-$1.70/lb | 50 lb bags | high-nitrogen |
| 15-5-10 Slow Release | $0.60-$1.20/lb | 50 lb bags | specialty |
| 6-2-0 Organic Fertilizer | $0.60-$0.80/lb | 32 lb bags | organic |
| 22-0-8 Winterizer | $1.50-$2.00/lb | 50 lb bags | specialty |
Synthetic balanced and high-N fertilizers cost more per pound but deliver more nutrient per pound, so the cost-per-1,000-sq-ft is often lower.
Organic fertilizers (like 6-2-0) look cheap per pound, but the low %N means you need much more product to hit the same 1 lb N target — so the total trip-to-the-store cost can be higher. Trade-off is improved soil biology over time.
Slow-release formulas command a premium per pound but reduce burn risk and cut the number of applications you need per year.
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NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K). The numbers represent the percentage of each nutrient by weight. For example, 10-10-10 means 10% nitrogen, 10% phosphorus, and 10% potassium.
Frequency depends on your grass type and season. Cool-season grasses typically need 3-4 applications per year (spring and fall), while warm-season grasses may need 4-5 applications during their growing season (spring through fall).
For cool-season grasses, apply in early spring and fall. For warm-season grasses, apply in late spring through early fall. Avoid fertilizing during extreme heat or drought conditions.
Yes, too much fertilizer can burn your lawn and cause environmental problems. Stick to the recommended amounts and avoid applying before heavy rain or on wet grass.
Choose based on your lawn's needs: High nitrogen (first number) for green color and growth, high phosphorus (middle number) for root development and new lawns, high potassium (last number) for stress resistance and winter hardiness.