Grass Seed Calculator
A 5,000 square foot lawn seeded at 6 pounds per 1,000 square feet needs about 31.5 pounds of grass seed, or 7 bags of 5-pound seed. Enter your lawn area and seeding rate to get an accurate estimate. The calculator factors in waste from wind, slopes, and uneven spreading so you buy the right amount the first time.
Quick answer
Seed needed equals lawn area divided by 1,000, multiplied by the seeding rate in pounds.
What this tells you
- •Seed needed equals lawn area divided by 1,000, multiplied by the seeding rate in pounds.
- •A waste factor (typically 5%) accounts for seed lost to wind, slopes, and uneven coverage.
- •Bags needed is the total seed weight rounded up to the nearest whole bag.
How to Use
- 1Measure or estimate your lawn area in square feet.
- 2Choose the seeding rate for your grass type and project (new lawn or overseeding).
- 3Enter the bag size you plan to buy.
- 4Set a waste percentage (5% is a good default for most lawns).
- 5Click Calculate to see total seed weight, bags needed, and coverage per bag.
How It Works
Formula
Seed Needed (lbs) = (Area / 1,000) x Seed Rate x (1 + Waste%)
Bags Needed = ceil(Seed Needed / Bag Size)
Coverage Per Bag (sq ft) = (Bag Size / Seed Rate) x 1,000The seeding rate is stated per 1,000 square feet, so the area is divided by 1,000 first. The waste multiplier adds a buffer for seed lost during spreading.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
New lawn, 5,000 sq ft
Overseeding a 2,500 sq ft yard
Grass Seed Needed by Lawn Size
Pounds of seed for common lawn sizes at new-lawn (6 lbs/1,000 sq ft) and overseeding (3 lbs/1,000 sq ft) rates, before waste.
| Lawn Size (sq ft) | New Lawn (6 lbs) | Overseeding (3 lbs) |
|---|---|---|
| 1,000 | 6 lbs | 3 lbs |
| 2,500 | 15 lbs | 7.5 lbs |
| 5,000 | 30 lbs | 15 lbs |
| 7,500 | 45 lbs | 22.5 lbs |
| 10,000 | 60 lbs | 30 lbs |
These figures assume flat ground with no waste. Add 5-10% for slopes, windy conditions, or bare patches.
New Lawn vs Overseeding: Which Rate Should You Use?
A brand-new lawn needs a heavier application because the seed must fill bare soil from scratch. Typical new-lawn rates run 4 to 8 pounds per 1,000 square feet depending on the grass species.
Overseeding fills in thin spots over existing turf. Because the established grass already covers part of the ground, you only need 2 to 4 pounds per 1,000 square feet.
Cool-season grasses like Kentucky Bluegrass and Tall Fescue tend toward the higher end of each range. Warm-season grasses like Bermuda and Zoysia often sit at the lower end because their seeds are smaller and spread more aggressively.
Always check the seed bag label for the manufacturer's recommended rate. If your lawn has heavy shade, steep slopes, or poor soil, bump the rate up by about 10-20% rather than doubling it.
Common mistakes
- Using the new-lawn rate when you are only overseeding, which wastes seed and can cause overcrowding
- Not adding extra seed for slopes where water runoff washes seed downhill before germination
- Seeding too thickly, which causes seedlings to compete for water and nutrients and leads to a weaker lawn
- Forgetting that different grass species have very different recommended rates per 1,000 square feet