Grass Seed Calculator

What this grass seed calculator does — and its lane

This tool is for broadcast seeding by weight: how much grass or lawn seed to buy for an area at a given rate, the everyday inversions of that rate, a general seed-rate mode for non-lawn crops, and a hydroseeding cost estimate. Seed is sold by the pound and the kilogram, so the one job here is turning a rate and an area into a weight — and back again. It is not a discrete-plant tool (that is the plant spacing calculator) and not a nutrient tool (the fertilizer calculator).

The real friction this fixes: bags quote a new-lawn rate, but most people are overseeding and should use about half — mix those up and you double your spend or smother existing turf. The mode has a new-vs-overseed toggle so the rate matches the job, and it shows the rate inversions people search for separately.

How much grass seed do I need?

Multiply your seeding rate (pounds per 1,000 square feet) by the lawn area divided by 1,000. That is the whole calculation; everything else is units.

seed (lb) = rate_{per 1,000 ft²} × (area_ft² ÷ 1,000)
per acre = rate × 43.56  ·  kg = lb × 0.453592
bags = round up(total lb ÷ bag weight)

So a 5,000 sq ft lawn at 6 lb per 1,000 sq ft needs 5 × 6 = 30 lb of seed; one acre at the same rate needs 6 × 43.56 ≈ 261 lb. The calculator accepts the area in square feet, square yards, square metres, acres or hectares (or as length × width), applies your grass type’s rate, halves it for overseeding, and gives pounds, kilograms and a bag count.

New seeding vs overseeding rates

A bare-ground new lawn needs the full rate; overseeding an existing lawn needs roughly half, because the established turf already provides cover and you only want to thicken it. The typical published new-seeding ranges below are a starting point — they vary with seed size and quality, so the seed tag wins. Pick a grass type to load an editable rate.

Tiny-seeded grasses like bluegrass and bentgrass cover an area with very few pounds; large-seeded tall fescue needs many more pounds for the same coverage. That is why coverage is always given by weight per area, not seeds.

Grass seed per square foot (and per square metre)

Two quick conversions people look up constantly:

lb of seed per sq ft = rate ÷ 1,000
sq ft per lb of seed = 1,000 ÷ rate
grams per m² ≈ rate × 4.882

At 6 lb per 1,000 sq ft that is 0.006 lb per square foot, one pound covers about 167 square feet, and the metric equivalent is roughly 29 grams per square metre. The “per sq ft / per lb” mode shows these live, with a small reference table for the common rates.

How many square feet does a pound of grass seed cover?

It is just the inverse of the rate: 1,000 ÷ rate. At 4 lb per 1,000 sq ft a pound covers 250 sq ft; at 6 lb it covers about 167 sq ft; at 10 lb (heavy tall-fescue new seeding) about 100 sq ft. So a 50 lb bag at 6 lb per 1,000 sq ft covers roughly 8,300 sq ft of new lawn — or twice that when overseeding.

Grass seed per acre

One acre is 43,560 sq ft, so the per-acre amount is the per-1,000 rate times 43.56. A typical 4–7 lb per 1,000 sq ft new-seeding rate works out to roughly 175–305 lb per acre. Enter the area in acres directly, or use the general seed-rate mode if your rate is already quoted in pounds per acre.

Seed rate for other crops

The general seed-rate mode covers anything quoted as a rate — pasture, cover crops, wildflower mixes — in pounds per acre, pounds per 1,000 sq ft or kilograms per hectare. It multiplies rate by area and, if you enter a germination or pure-live-seed percentage, divides by it so you buy enough viable seed:

seed to buy = (rate × area) ÷ (germination% ÷ 100)

Hydroseeding cost

Hydroseeding sprays a slurry of seed, mulch, fertilizer and a tackifier over the soil. It is normally priced per square foot for yards or per acre for larger sites. As a dated, illustrative 2026 ballpark it commonly lands around $0.06–$0.20 per square foot (roughly $2,000–$5,000 per acre), but that is an example that varies widely with size, slope, soil prep, seed blend and region — small jobs often hit a minimum fee and large sites get volume discounts, so always get a local quote. The cost mode multiplies your entered rate by the area; no price is baked in.