Calculator — Outdoor, Deck & Fence
Grass Seed Calculator
Pounds of grass seed for a new lawn, by grass type — with the seeding-rate table for every common grass.
Inputs
Results
Adjust the inputs to see your result.
About this calculator
Seed is specified by area — pounds per 1,000 sq ft — and the rate depends entirely on the grass: Bermuda seeds at 2 lb per 1,000 sq ft while ryegrass needs 8 lb, because Bermuda seeds are far smaller. This calculator applies the right rate for your grass type and converts the result to 25 lb bags.
What this number means
Grass seed is sold by weight, but it is specified by area: pounds per 1,000 sq ft, and the rate depends entirely on the grass. A pound of Bermuda seed covers far more ground than a pound of ryegrass because the seeds are far smaller — Bermuda seeds at 2 lb per 1,000 sq ft while ryegrass needs 8 lb for the same area. Using the wrong rate is the most common reason a new lawn comes up thin or, just as wastefully, far too thick.
The rates here are new-lawn rates. Overseeding an existing lawn uses roughly half the new-lawn rate, because the established grass fills in around the new seedlings. If your bag label gives a different rate for your exact blend, the label wins — blends with coatings or fillers change the effective rate.
The formula
- Area = Length × Width
- Pounds of seed = (Area ÷ 1,000) × seeding rate for the grass type
- 25 lb bags = Pounds ÷ 25, rounded up
- New-lawn seeding rate table (lb per 1,000 sq ft): Kentucky bluegrass 3, perennial ryegrass 8, tall fescue 7, Bermuda 2. Overseeding uses roughly half these rates.
Worked example
A 50 × 40 ft lawn (2,000 sq ft) seeded with tall fescue.
- Area = 50 × 40 = 2,000 sq ft
- Seed: (2,000 ÷ 1,000) × 7 = 14 lb
- Bags: 14 ÷ 25 = 0.56 → 1 × 25 lb bag
- For comparison, the same lawn in Bermuda would need only 4 lb; in perennial ryegrass, 16 lb.
Assumptions and limitations
- Rates are typical new-lawn rates for pure seed. Coated seed and seed blends follow the bag label, which may differ.
- Overseeding an existing lawn uses roughly half the new-lawn rate — halve the result if you are thickening, not starting, a lawn.
- Beds, paths, driveways and tree wells inside the measured rectangle must be deducted from the area first.
- Seed needs consistent moisture until germination: a thin lawn is more often a watering failure than a quantity failure.
Frequently asked questions
It depends on the grass: tall fescue at 7 lb per 1,000 sq ft needs 35 lb; Kentucky bluegrass at 3 lb needs 15 lb; perennial ryegrass at 8 lb needs 40 lb; Bermuda at 2 lb needs 10 lb. Pick your grass type in the calculator for the exact figure.
For a new lawn: Kentucky bluegrass 3 lb, perennial ryegrass 8 lb, tall fescue 7 lb, Bermuda 2 lb per 1,000 sq ft. Overseeding an existing lawn uses roughly half those rates.
Seed size. Bermuda seeds are tiny, so a pound contains far more seeds than a pound of large ryegrass seed. The rate is about seeds per square foot, not weight — weight is just how it is sold.
New-lawn rate for bare soil, overseeding rate (roughly half) for thickening an existing lawn. Seeding an existing lawn at the full new-lawn rate wastes seed and crowds seedlings so none establish well.
Far cheaper per square foot — a 2,000 sq ft lawn needs about 14 lb of tall fescue seed versus 200 rolls of sod. Seed takes weeks of watering and weed pressure to become a lawn, while sod is instant; the trade-off is time, not just money.
Split it into rectangles, work out each area, and add them. Deduct beds, paths and driveways from the total before running the calculator, or the seed quantity will be high.