Grass Seed Calculator
Sow too little grass seed and the lawn comes in thin and patchy; sow too much and seedlings crowd each other out and become prone to disease. The right amount depends mainly on the grass species, because seed sizes vary enormously – a pound of Kentucky bluegrass holds around ten times as many seeds as a pound of tall fescue. This grass seed calculator applies typical seeding rates for common cool- and warm-season grasses to your lawn area.
How to use this calculator
- Choose imperial or metric units and enter the lawn area by rectangle, circle or known area.
- Select your grass type. The calculator fills in a typical seeding rate in pounds per 1,000 square feet.
- Choose whether you are seeding a new lawn on bare soil or overseeding an existing lawn (roughly half the rate).
- If your seed bag lists a different rate, type it into the seeding rate box – the label always wins.
- Read the pounds and kilograms of seed to buy. Seed is sold in fixed bag sizes, so round up to the next bag.
The grass seed formula
Seed needed (lb) = lawn area (sq ft) ÷ 1,000 × seeding rate (lb per 1,000 sq ft). For metric users the calculator converts square meters to square feet (1 m² = 10.764 sq ft) and gives the answer in kilograms too. As a cross-check, 1 lb per 1,000 sq ft equals roughly 4.9 g per m².
Worked example
A 50 × 40 ft front yard is 2,000 sq ft. Seeding a new tall fescue lawn at 8 lb per 1,000 sq ft needs 2,000 ÷ 1,000 × 8 = 16 lb of seed. Overseeding the same lawn at 4 lb per 1,000 sq ft needs 8 lb. For Kentucky bluegrass at 3 lb per 1,000 sq ft, a new lawn of that size needs just 6 lb.
Typical seeding rates
The rates in the calculator are middle-of-the-range values from seed labels and university extension guides. Large-seeded bunch grasses such as tall fescue, perennial ryegrass and Bahia need about 6–10 lb per 1,000 sq ft for a new lawn. Fine fescues need around 4–5 lb. Kentucky bluegrass has tiny seeds and needs only 2–3 lb. Hulled Bermuda, zoysia and centipede are sown at roughly 1–2 lb, and many warm-season lawns are established from sod or plugs instead. Coated seed contains less actual seed per pound, so use the higher rate on the label.
When to sow
Cool-season grasses (fescues, ryegrass, bluegrass) establish best from late summer to early fall, when soil is still warm but air temperatures are falling and weeds are less competitive. Spring is a second-best window. Warm-season grasses (Bermuda, zoysia, centipede, Bahia, buffalo) need soil temperatures of about 65–70 °F (18–21 °C) and are sown in late spring to early summer.
Getting good germination
Loosen the top inch of soil, rake it level and spread seed in two passes at right angles using half the seed each time, which gives even coverage. Rake lightly so seed is no more than about ¼ inch deep, roll or tread it for good soil contact, then keep the surface consistently moist – light watering once or twice a day – until the new grass is about 2 inches tall. A thin layer of straw or compost helps hold moisture on slopes and sunny sites.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?
It depends on the species: about 6–10 lb for tall fescue or perennial ryegrass, 4–5 lb for fine fescue, 2–3 lb for Kentucky bluegrass, and 1–2 lb for hulled Bermuda or zoysia. Overseeding uses about half these rates.
How much grass seed for an acre?
An acre is 43,560 sq ft, so multiply the rate per 1,000 sq ft by 43.56. Tall fescue at 8 lb per 1,000 sq ft needs about 350 lb per acre.
Can I put down too much grass seed?
Yes. Overcrowded seedlings compete for light, water and nutrients, stay weak and are more likely to suffer from damping-off and other diseases. Stick close to the label rate.
How much seed do I need to overseed?
Usually about half the new-lawn rate, for example 3–4 lb of tall fescue or 1–1.5 lb of Kentucky bluegrass per 1,000 sq ft. Thin, patchy lawns may need closer to the full rate.
How long does grass seed take to germinate?
Perennial ryegrass can sprout in 5–10 days, tall fescue in 7–14 days and Kentucky bluegrass in 14–30 days. Warm-season grasses need warm soil and may take 2–3 weeks.