Grass Seed Calculator: How Much Seed and Fertilizer
Work out how much grass seed a lawn needs by grass type, new lawn or overseeding, in pounds and bags, plus the fertilizer for the same area. Add rectangles, circles and triangles or type the square feet, pick the grass and the job, and get pounds of seed with the extension range, bags and cost; the second tab turns the N-P-K on a fertilizer bag into pounds and bags.
Your numbers
Lawn area
Up to 6 areas, added together. Lengths in feet; a triangle's height is measured square to its base. Leave out beds, patios and the drive.
Grass and seeding rate
Leave empty to use 6.5 lb per 1,000 ft², the middle of 5 to 8 lb per 1,000 ft² (University of Tennessee Extension). Type the rate on your bag if it differs.
Bags and cost
Grass seed to buy
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- Bags (7 lb bag)
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- Across the extension range
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- Seeding rate used
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- Lawn area
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- Seed cost
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Seeding rates are for pure seed of one grass. Coated seed weighs more per seed, so follow the bag when it gives a higher rate.
The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.
How to work out grass seed
Seed is sold by the pound and sown by the pound per 1,000 square feet, so the sum is area × rate. Measure the lawn in feet and break it into rectangles, circles and triangles, or type the square footage if you know it. Leave out beds, patios and the drive. Then pick the grass and whether it is a new lawn or overseeding; the calculator uses the middle of the extension range unless you type the rate on your bag.
Worked example: a front lawn 50 × 40 ft (2,000 square feet) and a back lawn 100 × 50 ft (5,000), both new tall fescue. 7,000 ÷ 1,000 × 6.5 lb = 45.5 lb of seed, between 35 lb at the low rate and 56 lb at the high one. In 20 lb bags that is 3 bags; in 50 lb bags, one.
Seeding rates by grass type
The calculator's rates come from one table, University of Tennessee Extension's W160-B, so the grasses compare on the same basis. For a new lawn, in pounds per 1,000 square feet: Kentucky bluegrass 1 1/2 to 2, fine fescues (chewings, red and sheep) 3 to 5, tall fescue 5 to 8, perennial ryegrass 4 to 6. Warm-season grasses: common bermudagrass, hulled, 1/2 to 1 (double it for unhulled seed), centipedegrass 1/2 to 3 and Zoysia japonica 1/2 to 3.
Ranges differ between universities. Ohio State's turf program lists tall fescue at 8 to 10 lb and Kentucky bluegrass at 2 to 3, higher than Tennessee. Both are reasonable: the heavier rate fills in faster, while too much seed gives a crowded stand of weak seedlings. Mixes and blends print their own rate on the bag; pick Mix or blend and type it.
Warm-season lawns and St. Augustinegrass
St. Augustinegrass is planted as sod, plugs or sprigs, not as lawn seed, so the calculator gives no pounds for it. Use the Sod Calculator for the square feet and pallets instead. Bermudagrass, zoysiagrass and centipedegrass can be seeded, but they take longer to germinate and want warm weather: UT Extension gives air temperatures of about 68 to 95 °F for warm-season seed.
Overseeding means something different in the South. Bermudagrass lawns are sometimes overseeded with ryegrass in the fall for winter color; that is a separate job with its own rate, 5 lb of ryegrass per 1,000 square feet in Clemson's fact sheet, which also says it is not generally recommended for home lawns. Clemson's Home & Garden Information Center warns that the extra water, fertilizer and shade of overseeding can damage centipedegrass, zoysiagrass and St. Augustinegrass.
The fertilizer tab
Lawn fertilizer is labelled with three numbers, N-P-K, the percent by weight of nitrogen, phosphate and potash. Rates are set by nitrogen. Type the numbers from the bag and a nitrogen target, and the calculator divides: 1 lb of nitrogen from a 24-6-12 product takes 1 ÷ 0.24 = 4.17 lb of product per 1,000 square feet. It then scales to the lawn, counts bags and shows how many square feet one bag covers at that rate.
That last figure is a quick check against the bag. If the bag says it covers 5,000 square feet and the calculator says 12,000, the bag is set for a lighter feeding than your target, or the other way round. If the bag only gives a product rate, switch to The rate on the bag. LSU AgCenter applies 0.5 to 1 lb of nitrogen per 1,000 square feet at a time; a soil test tells you whether the lawn needs phosphate or potash at all.
For lawn care and landscaping crews
A seeding quote is built on the estimate visit: the size of each area, sun and shade, what grass is there now, whether it gets aerated first and what the customer wants it to look like by when. Most of it gets said out loud while you walk the yard, and the part that is not written down is the part that goes missing from the quote.
Sources, each read on 2026-10-24. All results are estimates; the seed bag, the fertilizer label and your soil test decide:
- University of Tennessee Extension W160-B, Turfgrass Establishment: Seeding (recommended seeding rate per 1,000 sq ft by species)
- Ohio State BuckeyeTurf: Turfgrass Establishment Series, Species/Cultivar Selection (seeding rates, 2023)
- NC State TurfFiles: Fall Renovation, Agronomics Part 2 (tall fescue rates for thin stands, 2021)
- Clemson HGIC 1206: Overseeding With Ryegrass (bermudagrass only; 5 lb per 1,000 sq ft)
- LSU AgCenter: Calculating Fertilizer Application Rates (0.5 to 1 lb N per 1,000 sq ft, worked example)
More for landscapers and lawn care pros: Landscaping sales, Door-to-door sales, Quote follow-up email.
The lawn gets measured on the estimate visit
The square footage, the shady corner and the grass the customer wants all get said out loud as you walk the yard. Record the visit in ParrotNotes and get a transcript, a summary and the action items, so the seeding quote is built from what was measured and agreed.
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