Lawn Seed Calculator
Getting the seed rate right matters: too little and you'll end up with a thin, patchy lawn, too much and you waste seed and risk overcrowding. New lawns sown on bare soil need a much denser rate than overseeding an established lawn, and UK sowing seasons — chiefly early autumn and mid-spring — affect how reliably that seed will germinate. Enter your lawn's dimensions below to get an instant estimate in kilograms and a practical bag-size suggestion.
Lawn area
50.0 m²
Seed needed
1.75 kg
Buy approximately
2 x 1kg
Based on a sowing rate of 35g/m² for a new lawn on bare soil. Buy a little extra to allow for edges, awkward corners and any thin patches you spot later.
Recommended for lawn care
Once you've sown your seed, here's what you'll need to keep your new lawn looking its best.
- Electric
- Small gardens
- 2 Years
£99.99
Pros
- 1200W motor for reliable cutting power
- 31-litre grass box
- Compact 32cm width suits small-mid gardens
Cons
- Corded — limited reach
- Cordless
- Small gardens
- 1 Year
£149.00
Pros
- Battery and charger included
- Lightweight and quiet
- Covers lawns up to 200m²
Cons
- Runtime limited by a single battery charge
- Petrol
- Large gardens
- 3 Years
£590.00
Pros
- Self-propelled 4-wheel drive
- Honda 4-stroke petrol engine
- Well-suited to larger lawns
Cons
- High upfront cost
- Requires fuel and maintenance
Frequently asked questions
When is the best time to sow grass seed in the UK?
The two best windows are early autumn (September to early October) and mid-spring (April to May), when the soil is warm and moist but temperatures aren't too extreme. Autumn is often considered ideal in the UK because there's less weed competition and more reliable rainfall.
How long does grass seed take to germinate?
Most UK grass seed mixes germinate within 7 to 21 days, depending on soil temperature, moisture and the seed mix used. Ryegrass tends to germinate fastest, while fine fescues can take a little longer.
Why do overseeding and new lawns need different seed rates?
A new lawn on bare soil needs a denser sowing rate (around 35g/m²) because every blade of grass has to establish from seed. Overseeding an existing lawn only needs to fill in gaps between healthy grass that's already there, so a lighter rate (around 25g/m²) is normally enough.
Should I buy a bit more seed than the calculator suggests?
Yes — it's a good idea to buy slightly more than the exact figure. Odd-shaped lawns, borders, edges and any patchy areas you top up later all use a bit of extra seed, and it's cheaper to have some left over than to run short mid-job.