How much grass seed you need

An even lawn needs the right amount of seed: too little leaves thin patches where weeds take hold, too much and the seedlings crowd each other out. This calculator starts from the area and the rate in grams per square metre, adds a margin for edges and awkward spots, and tells you how many packs to buy and how much seed to spread on each pass.

How the calculation works

• Seed: area in m² × rate in g/m² × (1 + margin), divided by 1,000 to get kg.
• Packs: kg of seed divided by the weight of one pack, rounded up.
• Passes: split the seed into two halves and spread them in two perpendicular directions for even coverage.

If your seed label gives a rate in pounds per 1,000 square feet, 1 lb per 1,000 ft² is about 4.9 g/m².

Seed needed by area

Indicative rates

The rate depends mostly on seed size: Kentucky bluegrass has tiny seeds and needs only a few grams, while tall fescue has large seeds and needs more. The rate printed on your mix's pack always takes priority.

The reading bands

• Below 15 g/m²: suitable only for very small seeds; with common mixes the lawn may stay thin.
• 15 to 25 g/m²: typical of overseeding.
• 25 to 50 g/m²: typical of a new lawn.
• Above 50 g/m²: higher than usual, seedlings that are too dense compete with each other.

Sowing tips

Sow when the soil is warm and moist: in many temperate climates early autumn and spring are the best times. Prepare the soil, spread the seed in two crossing passes, rake it in lightly and keep the ground moist until it germinates, which takes one to three weeks depending on the species. Store leftover seed somewhere cool and dry for patching.

Frequently asked questions

How much grass seed do I need for 50 m²?

At 35 g/m² with a 10% margin, about 1.93 kg: two 1 kg packs.

What is the rate for a new lawn?

With common mixes usually 25-40 g/m²; always follow the rate on the pack.

And for overseeding?

Usually 15-25 g/m², because the existing lawn already covers most of the soil.

Why sow in two passes?

Splitting the seed in half and spreading it in two perpendicular directions gives more even coverage.

What happens if I sow too thickly?

Seedlings compete for light, water and nutrients and the lawn grows weaker.

How much extra should I add?

5-10% is usually enough for edges, worn areas and small spreading errors.

How do I convert lb per 1,000 ft²?

Multiply by about 4.9 to get g/m²: 8 lb per 1,000 ft² is about 39 g/m².

Can I store leftover seed?

Yes, somewhere cool and dry; germination drops over time, so use it within one or two years.