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How much fertilizer do you actually need?

Start with the nitrogen you want to put down, not a rate off the bag. We work backwards to pounds of product, bags to buy, and what it costs you per thousand square feet.

What you're working with
One zone at a time — front and back rarely want the same thing.
ft²
Start here
Pounds of actual N per 1,000 ft². This is the only rate that means anything across two different bags.
lb N / 1,000 ft²
The three numbers on the front. Nitrogen is the one that does the work here.
N
–
P
–
K
lbs
Calculated for you · read only
engine v1.4.0
1bag to buy
0.31 bags exactly
Spread 15.6 lb of your 24-0-11 over 5,000 ft² to land exactly 0.75 lb of nitrogen per thousand.
Product to spread
15.6 lb
3.13 lb per 1,000 ft²
Actual nitrogen applied
3.75 lb N
across 5 × 1,000 ft²
One bag covers
16,000 ft²
at this nitrogen target
Left in the bag after
34.4 lb
keep it dry, it stores fine
Cost, this application
$11.88
Per 1,000 ft²
$2.38
Cost of nitrogen
$3.17
Phosphorus riding along
none
Potassium riding along
1.72 lb K
Bags are sold whole, so we round up to buy and tell you the leftover — we never round your rate.

These numbers come out of the same calculation engine that runs inside LawnDominator. The free tool and the app can't give you different answers.

Why this one is different

Four things every other fertilizer calculator gets wrong.

They ask for a rate

We ask for nitrogen

"3 lbs per thousand" means nothing until you know the analysis. A pound of nitrogen is a pound of nitrogen whether it comes from urea or a 6-4-0 bag.

They mix inputs and answers

Yours on the left, ours on the right

Nine identical boxes in one column and no clue which ones you're supposed to fill in. What you type is white and editable. What we calculate is dark and read-only.

They round to whole bags

We round the shopping, never the rate

Silently bumping you to two bags is how lawns get 1.4 lb of N in one pass. You get exact pounds to spread, bags to buy, and the leftover.

They hide the math behind an email

Show the math, take no address

Every step is one tap away and nothing is gated. If you want to check our arithmetic on paper, go ahead. That's the point.

One bag, one zone, one time. Your lawn needs this for every zone, all season.

LawnDominator runs this same math per zone, tracks your nitrogen totals as you log, and tells you when the next application is actually due, off growth potential and growing degree days rather than the calendar.

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In the app you also get
  • Season-to-date nitrogen per zone
  • Next application date from growth potential
  • Your shed, with true cost per application
  • Spray windows read off your local forecast