How much grass seed for 100 m²?
A new 100 square metre lawn sown with a general-purpose mix at about 24 g per m² needs roughly 2.44 kilograms of seed, or 3 bags of 1 kg. Overseeding would take about half that.
How to work it out
- 100 m² × 24 g = 2.44 kg
- 2.44 kg ÷ 1 kg per bag = 3 bags
UK and European lawn seed boxes usually quote a rate in grams per square metre, commonly somewhere around 25–50 g/m² for new lawns depending on the mix. Use the "rate from my seed bag" option if yours differs; ryegrass-heavy mixes are often sown heavier than this.
Adjust for your project
More options: Price · Purity · Germination …
- Seed needed
- 2.44 kg (5.38 lb)
- Seeding rate used
- 24 g per m²
- Straw to cover new seed (optional)
- About 24–37 kg of weed-free straw
- Starter fertilizer
- 1.95 kg of a 24-25-4 starter (≈5 g phosphate per m²)
- Cool-season grasses usually establish best from late-summer / early-fall seeding, with spring as a second choice.
- No weed-and-feed or crabgrass preventer around seeding. Most of them stop grass seed from sprouting too. Rutgers and UNH Extension: use only a weed product whose label says it is safe for newly seeded lawns, and read it before you buy.
- Straw is optional: use weed-free straw (not hay), spread thin and even. It keeps the seed damp and stops it washing off slopes.
- More seed isn’t better — overcrowded seedlings compete and thin out. Good seed-to-soil contact and steady moisture matter more.
Boxes of seed for a new 100 m² lawn, by box size
| Box or bag size | Bags to buy |
|---|---|
| 1 kg | 3 bags |
| 1.5 kg | 2 bags |
| 3 kg | 1 bag |
| 10 kg | 1 bag |
| 20 kg | 1 bag |
What to know about sowing a 100 m² lawn
A hundred square metres is about 1,076 sq ft, a typical back garden lawn of 10 × 10 m or 8 × 12.5 m. At around 24 g/m² it takes two and a half 1 kg boxes, so buy three, or a single larger bag if the price per kilo is better. Leftover seed keeps for a season or two in a cool, dry place, though germination slowly falls.
Weigh it out rather than guess. Mark the lawn into 1 m strips with string or canes, weigh the seed for one strip on a kitchen scale, and use a cup or yoghurt pot as a measure for the rest. Sow half the seed along the strips and half across them.
The most common mistake with small lawns is sowing too thickly "to be safe". Crowded seedlings are weaker and more prone to damping off. If the box gives a rate for new lawns and another for patching, use the new-lawn rate for bare soil and the lower one over existing grass.
The US figures work the same way per 1,000 sq ft: see how much grass seed for 1,000 sq ft of tall fescue.
Different size? Use the full Grass Seed Calculator.
What you’ll need
- Handheld spreaderBudget price
A hand-crank spreader for seed and fertilizer on small lawns and patches.
See options on Amazon (opens in a new tab) - Bow rake / landscape rakeBudget price
Steel tines for spreading gravel and soil and leveling it flat. The flat back of a bow rake doubles as a leveling tool.
See options on Amazon (opens in a new tab) - Lawn roller (fill with water)Mid-range price
Presses new sod and seed into the soil. Fill it partway — you want contact, not compaction.
See options on Amazon (opens in a new tab)
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Frequently asked questions
How much grass seed to overseed 100 m² of lawn?
About 1.46 kilograms at 15 g per m², roughly half the new-lawn amount.
My seed box says 35 g per m². How much for 100 m²?
3.5 kilograms: 100 × 35 g. That is 4 bags of 1 kg.
How much tall fescue seed for a 100 m² lawn?
About 2.93 kilograms at 29 g per m²: fescue seed is large, so it is sown heavier than a fine mix.
Other common sizes
Sources
- Penn State Extension: Turfgrass Seed and Seed Mixtures (opens in a new tab) — Seeding rates for bluegrass (2–3 lb), tall fescue (6–8 lb), fine fescue; pure live seed adjustment
- NC State Extension Gardener Handbook, Ch. 9: Lawns (opens in a new tab) — Seeding rates incl. bermuda and zoysia 1–2 lb, centipede 0.25–0.5 lb per 1,000 sq ft
- NC State Extension: Tall Fescue and Kentucky Bluegrass Home Lawn Calendar (opens in a new tab) — Tall fescue at 6 lb per 1,000 sq ft; Kentucky bluegrass added at 1–2 lb
- Rutgers NJAES FS584: Seeding Your Lawn (opens in a new tab) — Bluegrass about 2 lb, tall fescue 4–6 lb per 1,000 sq ft; weed-free straw 50–90 lb (1–2 bales) per 1,000 sq ft; use only herbicides labeled for newly seeded lawns
- UNH Cooperative Extension: Starting & Overseeding Lawns (opens in a new tab) — Weed-free straw, about 1 bale per 1,000 sq ft, over new seedings; renovation (overseeding) works best when more than half the lawn is still good turf; power-rake thatch first; some crabgrass herbicides can only be used on mature turf, not new seedings
- UC IPM Healthy Lawns: Starter fertilizer (opens in a new tab) — At planting: at least 1 lb P and no more than 1 lb N per 1,000 sq ft
- UMass Soil and Plant Nutrient Testing Lab: Fertilizer Guide for Lawns (opens in a new tab) — Common starter 24-25-4; new-lawn phosphate from soil test (0.5 lb P₂O₅ per 1,000 sq ft in its example)
- LSU AgCenter: Pure Live Seed Calculation (opens in a new tab) — PLS = purity × germination; seed needed = PLS rate ÷ PLS; ryegrass overseeding rates in lb PLS
- UConn Home & Garden Education Center: Understanding Grass Seed Labels (opens in a new tab) — Coating weight is shown on the label (example: 50% of the bag); purity × germination = live seed
- Clemson HGIC 1206: Overseeding With Ryegrass (opens in a new tab) — Ryegrass into dormant bermuda: 5 lb per 1,000 sq ft on established lawns, 10 lb on bare areas; mow close and catch clippings; overseeding damages centipede, zoysia and St. Augustine
- UT Extension W161-J: Overseeding Bermudagrass with Perennial Ryegrass (opens in a new tab) — Initial overseeding 10–15 or more lb per 1,000 sq ft; sports turf may exceed 20 lb a season
- University of Arizona AZ1683: Overseeding Winter Grasses into Bermudagrass Turf (opens in a new tab) — Ryegrass at 12–15 lb per 1,000 sq ft; don’t scalp; St. Augustine and zoysia not suited to overseeding