Lawn Fertilizer Calculator

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Written By: Mark Marino

a Massachusetts Core Applicator License holder and owner/operator of Lawn Phix,

Updated on


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How to use this lawn calculator (fertilizer rates):

  1. Type the square feet of your lawn
  2. Type the total pounds of Nitrogen (N) you wish to apply per 1,000 sq ft
    1. (Note, this calculator can also be used for both Phosphorus and Potassium, N-P-K, fertilizer)
  3. Type the Nitrogen (N) percentage located on your bag of fertilizer
    1. eg: 6-4-0 for Milorganite (type 6)
  4. Click “Calculate”


Your square footage is required

Desired Nitrogen per 1,000 is needed

% of Nitrogen in fertilizer is needed

More Lawn Care Calculators

Proper Nitrogen (N), Phosphorus (P), and Potassium (K) fertilizer applications (N-P-K) on your lawn are crucial to the year-long success of your turf. Add too much nitrogen at the wrong time, and your lawn could burn. Add too little over the course of a year, and signs of your underfed turf – not thick, green, or healthy-looking – will show.

A very common lawn care question is around fertilizer recommendations – ‘how much fertilizer to apply per year?’ Or ‘how much fertilizer to apply per acre or per sq ft?’. A good rule of thumb is to apply 3-4 pounds of nitrogen fertilizer to your lawn every year. Depending on the results of your soil test , and the number of times you apply lawn fertilizer throughout the year will dictate how much nitrogen needs to be applied with each feeding, but 3-4 pounds per 1,000 sq ft is a basic guideline.

The same goes for the other essential macronutrients in fertilizer – Phosphorus, and Potassium. A good maintenance lawn fertilizer will include a 3-1-2 or 4-1-2 ratio; the first three numbers are located on the fertilizer bag (Nitrogen – Phosphorus  – Potassium, or N-P-K). 

If you’re using a 4 Step plan, then aiming for approximately one pound of nitrogen per 1,000 sq ft is the goal. But if you choose to spoon-feed more frequently, then anywhere between 0.25 and 0.5 pounds of nitrogen per 1,000 square feet (sq ft) per fertilizer application is ideal (or “lbs n. 

So how do you know how much nitrogen, phosphorus, and potassium fertilizer you’re applying? This fertilizer calculator will do the trick. You can use our nitrogen calculator to determine how much nitrogen is in each bag of the fertilizer of choice.

Next, find the square footage of your lawn. One of my favorites is from Sod Solutions.

Then, use this lawn fertilizer calculator. Plugin your lawn square footage, desired amount of nitrogen to be delivered per 1,000 sq ft, and the nitrogen percentage on the bag of your lawn fertilizer. 

How To Calculate Lawn Fertilizer per 1,000 Square Feet

  1. Nitrogen percentage ÷ 100 (e.g. Milorganite “6” = 0.06)
    1. n
  2. else total = b / ( c / 100 ) * a / 1000;

The formula looks like this… if I want to apply 1 pound of Nitrogen on my 5,000 sq ft lawn and using Milorganite fertilizer as a guide:

Desired Nitrogen weight ÷ (Nitrogen percentage ÷ 100) x your lawn’s square feet ÷ 1,000

1 ÷ (6 ÷ 100) x 5,000 ÷ 1,000 = 83.3 pounds of total Milorganite fertilizer to cover my 5,000 square feet lawn – or about 2.5 total bags of the 32 pounds Milorganite nitrogen fertilizer. 

This can be used for N-P-K. It’s suggested to get a soil test at the beginning of each season

I hope this lawn fertilizer calculator is helpful! Please let me know by commenting below.

If you have any questions or see any bugs in this lawn fertilizer calculator, please contact me

Lawn Fertilizer Calculator FAQs

How do I calculate how much fertilizer I need?

You first need a soil test at the beginning of each growing season. Once you have the results of your Nitrogen, Phosphorus, Potassium (N-P-K) levels will dictate how much fertilizer to apply (pounds per 1,000 square feet). Use our lawn fertilizer calculators to help guide you.

How much area does a 50 lbs bag of fertilizer cover?

That all depends on the N-P-K ratios on the fertilizer bag and its application rate. If you want to deliver 0.7 lbs N per 1,000 sq ft and the N percentage on the label is 28, you will 2.5 lbs of fertilizer per 1,000 sq ft. Always follow the label and use our fertilizer calculators to help with the quick math.

How do you calculate pounds of fertilizer per acre?

There are 43,560 square feet per acre, so type 43560 in our fertilizer calculator, followed by the total lbs N per 1,000 sq ft you wish to apply, and lastly the Nitrogen percentage on the bag/label. For example, you will want to apply a total of ~120 lbs of fertilizer with a 18% Nitrogen percentage per acre to deliver 0.5 lbs N per 1,000.

Author's Note: this piece has been updated for accuracy since its first publication on
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Author: Mark Marino
My name is Mark Marino, and I am the founder, owner, and operator of Lawn Phix. With a passion for lawn care and turf nutrition for over a decade, I've dedicated countless hours to correcting soil and perfecting lawns. Today, my expertise, backed by formal courses at UMass Extension Pesticide Education, allows me to offer top-tier lawn care services and advice. I am a fully licensed and insured lawn care applicator in Massachusetts, specializing in comprehensive turf nutrition, weed control, and lawn pest control. My license number is AL-0053865. Contact me at [email protected] or +1 (508) 500-8402.

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