Grass Seed & Lawn Fertilizer Calculator
Seed a new lawn, overseed a thin one, or feed it right. Get pounds of seed for your grass type and the amount of fertilizer to spread based on the nitrogen in the bag.
Grass seed
How to use the grass seed calculator
- Measure your lawn area in square feet (length × width for each section).
- Choose the grass type and whether you are starting a new lawn or overseeding.
- For fertilizer, enter the first number of the N-P-K label and the bag size; 1 lb of nitrogen per 1,000 sq ft per feeding is a common target.
Seeding rates and fertilizer math
Seeding rates vary hugely by grass type because seed sizes differ. Tall fescue needs about 6–8 lb per 1,000 sq ft for a new lawn, Kentucky bluegrass only 2–3 lb, and hulled Bermuda 1–2 lb. Overseeding uses about half the new-lawn rate. Sowing far more than recommended makes seedlings compete and can weaken the lawn.
Seed cool-season grasses (bluegrass, fescue, ryegrass) in late summer to early fall, when soil is warm and air is cooler; warm-season grasses (Bermuda, zoysia, centipede, buffalograss) in late spring. Keep the top inch of soil moist until seedlings are established. St. Augustine is usually planted as sod or plugs rather than seed.
Fertilizer is measured by nitrogen. Product needed = nitrogen target ÷ nitrogen percentage × area ÷ 1,000. A 29-0-4 bag applied at 1 lb N per 1,000 sq ft needs about 3.4 lb of product per 1,000 sq ft. Follow the label and local rules, avoid fertilizing before heavy rain, and sweep granules off pavement.
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Frequently asked questions
How much grass seed per 1,000 sq ft?
About 6–8 lb for tall fescue, 2–3 lb for Kentucky bluegrass, 5–7 lb for perennial ryegrass and 1–2 lb for hulled Bermuda for a new lawn.
How much seed for overseeding?
Roughly half the new-lawn rate.
What do the fertilizer numbers mean?
N-P-K: the percentage by weight of nitrogen, phosphate and potash in the bag.
How often should I fertilize?
Cool-season lawns commonly get 2–4 feedings a year, heaviest in fall; warm-season lawns are fed in late spring and summer.