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Lawn Fertilizer Calculator — How Much

Calculate the right amount of fertilizer for your lawn

Units

Fertilizer Needed

50.0 lbs

Bags

1

Cost

$25

Coverage/Bag

5,000 sq ft

Current ratio: 10-10-10

Typical range: 0.5 - 1.5 lbs N per 1,000 sq ft per application

Fertilizer: 50.0 lbs

1 bag of 50 lb

Bags

1

50 lb bags

Coverage/Bag

5,000

sq ft

Est. Cost

$25

total

N-P-K

10-10-10

Nutrients Delivered

Nitrogen (N)5.0 lbs
Phosphorus (P)5.0 lbs
Potassium (K)5.0 lbs

N-P-K Ratio

Nitrogen (N) 10%10%
Phosphorus (P) 10%10%
Potassium (K) 10%10%

Coverage

5,000 of 5,000 sq ft coverage100%

Each bag covers ~5,000 sq ft at your rate

Example Calculations

1Spring Lawn Feeding (5,000 sq ft)

Inputs

Lawn area5,000 sq ft
Fertilizer10-10-10 (general purpose)
N rate1.0 lb per 1,000 sq ft
Bag size50 lb

Result

Fertilizer Needed50.0 lbs (1 bag)
Nitrogen Delivered5.0 lbs
Phosphorus Delivered5.0 lbs
Potassium Delivered5.0 lbs

(5,000/1,000) × 1.0 / 0.10 = 50 lbs of 10-10-10 fertilizer. One 50 lb bag provides even nutrient coverage.

2High-Nitrogen Summer Feed (8,000 sq ft)

Inputs

Lawn area8,000 sq ft
Fertilizer32-0-4 (lawn maintenance)
N rate1.0 lb per 1,000 sq ft
Bag size50 lb

Result

Fertilizer Needed25.0 lbs (1 bag)

(8,000/1,000) × 1.0 / 0.32 = 25 lbs. Higher nitrogen percentage means less product needed.

Frequently Asked Questions

Q

How much fertilizer do I need for my lawn?

The amount depends on your lawn area, fertilizer N-P-K ratio, and desired nitrogen rate. For example, a 5,000 sq ft lawn using 10-10-10 fertilizer at 1 lb N per 1,000 sq ft needs 50 lbs of fertilizer (one 50 lb bag). Higher nitrogen percentages mean less product needed per application.

Q

What does N-P-K mean on fertilizer bags?

N-P-K stands for Nitrogen-Phosphorus-Potassium, the three primary plant nutrients. A 10-10-10 fertilizer is 10% nitrogen, 10% phosphorus, and 10% potassium by weight. Nitrogen promotes leaf growth, phosphorus supports root development, and potassium improves overall plant health and disease resistance.

Q

How much nitrogen should I apply per application?

Apply 0.5 to 1.0 lb of nitrogen per 1,000 sq ft per application. Never exceed 1.5 lbs per 1,000 sq ft in a single application to avoid burning. Cool-season grasses typically need 2-4 lbs total nitrogen per year, split into 3-4 applications. Warm-season grasses need 2-6 lbs total per year.

Q

When should I fertilize my lawn?

Cool-season grasses (fescue, bluegrass, ryegrass): fertilize primarily in fall (September-November) with a lighter spring application. Warm-season grasses (Bermuda, Zoysia, St. Augustine): fertilize in late spring through summer (May-August). Avoid fertilizing during extreme heat or drought.

Q

What is the best fertilizer ratio for lawns?

For established lawns, use a high-nitrogen ratio like 20-5-10 or 32-0-4. For new lawns or overseeding, use a balanced starter fertilizer like 10-10-10 or 16-4-8. For fall winterizing, use a potassium-heavy ratio like 15-0-15. Soil tests can identify specific nutrient deficiencies.

Q

Can I use too much fertilizer?

Yes. Over-fertilizing causes fertilizer burn (brown, crispy grass), promotes thatch buildup, increases disease susceptibility, and contributes to water pollution through runoff. Always follow recommended application rates and water lightly after applying to help nutrients reach the soil.

See Also

  • Rain Barrel Calculator

    Calculate rainwater harvesting capacity

  • Irrigation Calculator

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  • Mulch Calculator

    Calculate mulch for landscaping

  • Soil Calculator

    Calculate soil for garden projects

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Last Updated: Feb 13, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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