Key takeaways
- Ohio State's new-lawn seeding rates run from 2 to 3 lb per 1,000 sq ft for Kentucky bluegrass to 8 to 10 lb for tall fescue.
- Fertilizer per 1,000 sq ft = target pounds of nitrogen ÷ the bag's nitrogen percentage, so 0.75 lb of N from 16-8-8 is 4.69 lb.
- Purdue advises no more than 1 lb of nitrogen per 1,000 sq ft in a single application.
Enter your lawn's area, pick a grass type, and say whether you're seeding a new lawn or overseeding. For fertilizer, enter the first number on the bag, the pounds of nitrogen you want to put down per 1,000 square feet, and the bag's weight. The tool gives pounds of seed, pounds of fertilizer and how many bags to buy.
How the calculator works
Seed (lb) = area ÷ 1,000 × seeding rate
For overseeding, the tool multiplies the rate by an overseed factor. The default is 0.5. That's a rule of thumb, not a figure we found from an extension service, so change it if your seed bag or local extension office says otherwise.
Fertilizer per 1,000 sq ft (lb) = target lb of nitrogen ÷ (nitrogen % ÷ 100)
Total fertilizer (lb) = fertilizer per 1,000 sq ft × area ÷ 1,000
Bags = total fertilizer ÷ bag weight, rounded up
The fertilizer formula is the one Purdue University's turf program uses. It works from nitrogen because lawn rates are set in pounds of nitrogen, not pounds of product.
Seeding rates by grass type
The presets come from Ohio State's turfgrass establishment series, for new lawns. We've added the totals for two common lawn sizes.
| Grass | Rate per 1,000 sq ft | 5,000 sq ft | 8,000 sq ft |
|---|---|---|---|
| Kentucky bluegrass | 2 to 3 lb | 10 to 15 lb | 16 to 24 lb |
| Perennial ryegrass | 7 to 8 lb | 35 to 40 lb | 56 to 64 lb |
| Tall fescue | 8 to 10 lb | 40 to 50 lb | 64 to 80 lb |
| Fine fescues | 3 to 6 lb | 15 to 30 lb | 24 to 48 lb |
For a mix, the bag usually prints its own rate. Use that rather than any one species.
Worked example
Purdue's example: an 8,000-square-foot lawn, 16-8-8 fertilizer, and a target of 0.75 pounds of nitrogen per 1,000 square feet.
- Nitrogen share: 16 ÷ 100 = 0.16
- Per 1,000 sq ft: 0.75 ÷ 0.16 = 4.69 pounds of product
- Whole lawn: 4.69 × 8,000 ÷ 1,000 = 37.5 pounds
Purdue's page rounds that to 37 pounds. If your bag holds 20 pounds, 37.5 ÷ 20 = 1.9, so you'd buy 2 bags.
For seed on the same lawn, overseeding tall fescue:
- New-lawn rate: 8 to 10 pounds per 1,000 sq ft
- Overseed at 0.5: 4 to 5 pounds per 1,000 sq ft
- Whole lawn: 8 × 4 = 32 to 8 × 5 = 40 pounds
How much nitrogen to target
The 0.75 in the example is Purdue's example input, not a recommendation for your lawn. For cool-season lawns, Purdue's guide to fertilizing cool-season lawns says:
- "In general, do not apply more than 1 pound of nitrogen per 1,000 square feet in a single application."
- Well-maintained lawns need 3.5 to 4 pounds of nitrogen per 1,000 square feet a year, and low-maintenance lawns 1 to 3 pounds.
Warm-season grasses and other regions follow different calendars, so check with your state's extension office. Also check whether your state or town has rules on lawn fertilizer before you buy.
What the three numbers mean
The numbers on the bag are nitrogen, phosphorus and potassium, as percentages of the bag's weight. The formula only uses the first. Purdue's guide says most established lawns have adequate phosphorus, that a soil test is the only way to know for sure, and that you might need phosphorus in the bag when seeding.
Measuring your lawn
Break the lawn into rectangles, multiply length by width for each, and add them. Leave out the house, driveway, patio and planting beds. For a curved edge, a rectangle that roughly matches is close enough for a seed or fertilizer order. The figures here are per 1,000 square feet, so a measuring error scales straight into the order.
Laying sod instead
Sod is sold by the roll or the pallet, and pallet sizes vary by supplier. Divide your lawn's area by the square feet your supplier quotes per pallet, and round up. We don't give a standard pallet size because we found no source for one.
Common mistakes
- Treating the bag's numbers as pounds. 16-8-8 means 16 percent nitrogen, so a 20-pound bag holds 3.2 pounds of nitrogen.
- Using a per-acre rate as a per-1,000 rate. An acre is 43,560 square feet, so the numbers are very different.
- Seeding a mix at a single species' rate. Use the rate on the mix's own label.
- Counting beds and paths in the area. It inflates the order and wastes fertilizer where nothing needs it.
- Taking our overseed factor as research. The 0.5 default is a rule of thumb, so follow your label or extension office where they differ.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
For a new lawn, Ohio State gives 2 to 3 pounds for Kentucky bluegrass, 3 to 6 for fine fescues, 7 to 8 for perennial ryegrass and 8 to 10 for tall fescue.
How much seed do I need to overseed?
A common rule of thumb is about half the new-lawn rate. We didn't find an extension figure for it, so check the rate on your seed bag.
How do I work out how much fertilizer to use?
Divide the pounds of nitrogen you want per 1,000 square feet by the bag's nitrogen percentage as a decimal. Then multiply by your area in thousands of square feet.
How much 16-8-8 do I need for 8,000 square feet?
At 0.75 pounds of nitrogen per 1,000 square feet, about 4.69 pounds per 1,000, or 37.5 pounds for the whole lawn.
How much nitrogen should I put down at once?
Purdue's guide for cool-season lawns says no more than 1 pound of nitrogen per 1,000 square feet in a single application.
How much sod do I need?
Measure the area, then divide by the coverage your supplier gives for a pallet or roll. Pallet sizes vary, so ask before you order.
Sources
We use primary sources where we can: building codes, federal rules and manufacturer documents. Read our editorial standards.
- Ohio State University: Turfgrass establishment series, species and cultivar selection
- Purdue University: Calculating the pounds of fertilizer to apply
- Purdue Extension: A simple procedure for fertilizing cool-season lawns