Fertilizer Calculator: How Much Does Your Lawn Need?
Enter your lawn size and the numbers on your fertilizer bag — we'll tell you exactly how many pounds and bags to buy, and the spreader setting to use. The rule of thumb: 1 pound of nitrogen per 1,000 sq ft per feed.
Top-rated lawn fertilizers
Verified, Amazon-available picks to match your number above.
Scotts Turf Builder WinterGuard 32-0-10
Beginner friendlyScotts Turf Builder Starter Food for New Grass
Beginner friendlySimple Lawn Solutions Fall Lawn Booster 3-18-18
Beginner friendlySimple Lawn Solutions Liquid Potassium 0-0-25
Beginner friendlyAs an Amazon Associate, Measure Lawn earns from qualifying purchases.
Spreaders to apply it evenly
Chapin 8401C International Chest-Mount Spreader
Beginner friendlyRecommended for lawns under 5,000 sq ft. Hands-free chest-mount design for easy spreading of fertilizer seed and granular products.
Scotts Turf Builder Classic Drop Spreader
Beginner friendlyAs an Amazon Associate, Measure Lawn earns from qualifying purchases.
How to work out how much fertilizer you need
Fertilizer is sized by nitrogen — the first of the three NPK numbers on the bag. Turf wants about 1 lb of actual nitrogen per 1,000 sq ft per application. Because a bag is only part nitrogen, you spread more product than that to hit the target:
Total product = (lawn area ÷ 1,000) × product per 1,000
Bags = total product ÷ bag weight, rounded up
Example: a 16-4-8 fertilizer is 16% nitrogen, so you need ~6.25 lb of product per 1,000 sq ft. On a 5,000 sq ft lawn that's ~31 lb — one 50-lb bag.
Measure your real mowable lawn free on satellite imagery in 2 minutes — then your fertilizer numbers are exact.
Measure my lawn free →Fertilizer questions, answered
How much fertilizer do I need per 1,000 sq ft?
The standard is 1 pound of actual nitrogen per 1,000 sq ft per application. The amount of product that takes depends on the first NPK number: divide 1 by that number as a decimal. A 16-4-8 fertilizer (16% N) needs about 6.25 lb of product per 1,000 sq ft; a 32-0-4 needs about 3.1 lb.
How many bags of fertilizer do I need?
Work out the total pounds of product (lawn area ÷ 1,000 × pounds-per-1,000), then divide by the bag weight and round up. For example, 5,000 sq ft with a 16-4-8 fertilizer needs ~31 lb of product — one 50-lb bag, or three 12.5-lb bags.
What do the three fertilizer numbers (NPK) mean?
They are the percentages of Nitrogen, Phosphorus and Potassium by weight. A 16-4-8 bag is 16% nitrogen, 4% phosphorus, 8% potassium — the rest is filler and other nutrients. Nitrogen (the first number) is what drives green growth and what you size your application around.
Can I apply too much fertilizer?
Yes. Exceeding about 1 lb of nitrogen per 1,000 sq ft in a single feed of quick-release fertilizer can burn the lawn (brown streaks). Slow-release products are more forgiving. When in doubt, apply less and feed again in 4–6 weeks.