What is the best time to seed a lawn?

The best time to seed a lawn depends on the grass type. For cool-season grasses (fescue, ryegrass, bluegrass), seed in early autumn (September-October) or spring (March-April). For warm-season grasses (bermuda, zoysia), seed in late spring to early summer (May-June) when soil temperatures are consistently above 18°C (65°F).

Grass Seed Calculator — How Much Seed Do You Need?

Calculate Your Grass Seed

Enter your lawn dimensions and we'll tell you exactly how much seed to buy.

Measurement Unit

Length (metres)

Width (metres)

Grass Type

Seeding Type

Your Results

Lawn Area

—

Seed Needed

—

With 10% Extra

—

Get Your Free Lawn Care Calendar

We'll send you a personalised monthly guide on when to seed, feed, and mow — based on your region.

No spam. Unsubscribe anytime. We respect your inbox.

Grass Seed Coverage Rates by Type

Different grass varieties require different amounts of seed per square metre. The table below shows the recommended seeding rates for the most common grass types, for both new lawns and overseeding.

Grass Type	New Lawn (g/m²)	Overseeding (g/m²)	New Lawn (lbs/1000ft²)
Perennial Ryegrass	40–50	20–25	6–8
Fine Fescue	25–35	15–20	4–5
Tall Fescue	35–45	20–25	6–8
Kentucky Bluegrass	20–30	10–15	2–3
Bermuda Grass	15–25	10–15	1–2
UK Lawn Mix	35–50	20–25	5–7
US All-Purpose Mix	35–45	20–25	5–7

How to Use This Grass Seed Calculator

Getting the right amount of grass seed doesn't need to be complicated. Here's how to use this tool and get an accurate result every time.

Step 1: Measure Your Lawn

Use a tape measure or pace out the length and width of the area you want to seed. For irregular shapes, break the area into rough rectangles and add them together. If you already know your total square metreage (or square footage), enter any length and width combination that equals that area.

Step 2: Choose Your Grass Type

Perennial Ryegrass is the most common choice in the UK — it's hard-wearing, germinates quickly, and looks great in most lawns. If your lawn gets a lot of shade, Fine Fescue is a better option. In warmer climates (US South), Bermuda Grass is the standard.

Step 3: New Lawn or Overseeding?

Starting from bare soil? Select "New Lawn" — you'll need more seed to establish full coverage. If you're thickening up an existing lawn with thin patches, "Overseeding" uses about half the amount. For small bare spots, "Patching" uses a higher rate to ensure quick coverage in concentrated areas.

Step 4: Add 10% Extra

Our calculator automatically includes a 10% buffer. This accounts for uneven spreading, seed that birds eat, and areas near edges where you'll want heavier coverage. It's always better to have a little extra than to run short mid-project.

Frequently Asked Questions

How much grass seed do I need per square metre?

For a new lawn, you typically need 35–50 grams of grass seed per square metre, depending on the grass type. For overseeding an existing lawn, use 15–25 grams per square metre. Fine fescue requires less seed (25–35g/m²) while ryegrass needs more (40–50g/m²).

How much grass seed do I need per square foot?

For a new lawn, plan on roughly 3–5 pounds per 1,000 square feet for most grass types. Kentucky Bluegrass needs about 2–3 lbs per 1,000 sq ft, while Tall Fescue and Ryegrass need 6–8 lbs per 1,000 sq ft. Our calculator gives you a precise figure based on your chosen grass type.

When is the best time to seed a lawn in the UK?

The ideal time to sow grass seed in the UK is early to mid-autumn (September to October), when the soil is still warm from summer but rainfall is increasing. Spring (March to April) is the second-best window. Avoid sowing in winter or during hot, dry summer periods.

Should I overseed or start a new lawn?

If more than 50% of your lawn is still healthy grass, overseeding is usually the best approach — it's cheaper, quicker, and less disruptive. If your lawn is mostly bare soil, weeds, or moss, starting fresh with a new lawn will give better long-term results. Our calculator adjusts the seed amount based on your choice.

Can I use too much grass seed?

Yes. Over-seeding (using significantly more than recommended) causes seedlings to compete for light, water, and nutrients, leading to weak, thin grass that's prone to disease. Stick to the recommended rates — more seed doesn't mean a better lawn.

How long does grass seed take to grow?

Perennial Ryegrass germinates in 5–10 days and is the fastest. Fine Fescue takes 10–14 days, and Kentucky Bluegrass can take 14–30 days. Full establishment (a lawn that's ready for regular use) typically takes 8–12 weeks regardless of the variety.