Grass Seed Calculator
Estimate the kilograms of grass seed and the number of bags you need by entering your lawn dimensions and a seeding rate.
m
m
Measurement units
Lawn type
g/m²
kg
Buy 1 bag
- 1
Lawn area
10 × 6 = 60 m² - 2
Effective seeding rate
35 = 35 g/m² - 3
Seed weight (g)
60 × 35 = 2,100 g - 4
Seed weight (kg)
2,100 ÷ 1000 = 2.10
How does this calculator work?
Multiply your lawn area in square metres by the seeding rate to get the seed weight. A new lawn needs about 35 g/m²; overseeding needs about half that. Divide the total by your bag weight and round up to find how many bags to buy.
Formula
How this is calculated
Enter the length and width of the area you want to sow and choose whether the measurements are in metres or feet. The calculator multiplies length by width to find the lawn area, converting square feet to square metres (1 ft² = 0.0929 m²) when needed.
The seeding rate is how much seed to spread per square metre. A new lawn typically needs about 35 g/m² (roughly 0.7 lb per 100 sq ft) for good coverage, while overseeding an existing lawn uses about half that rate because the established grass already provides cover. The total seed weight is area multiplied by the effective rate, reported in grams, kilograms and pounds.
To find how many bags to buy, the seed weight in kilograms is divided by the bag weight and rounded up, since you cannot buy a fraction of a bag. Rates vary by grass species and soil conditions, so treat the figure as a starting point and check the supplier’s recommendation on the packet.
Frequently asked questions
A new lawn usually needs about 35 grams of seed per square metre. When overseeding an existing lawn, roughly half that amount (around 17–18 g/m²) is normally enough.
Overseeding adds seed to a lawn that already has grass, so you only need to fill gaps and thicken coverage. About half the new-lawn rate is typical.
It is wise to round up and keep a little spare for patchy spots or re-sowing. The calculator already rounds the number of bags up to the next whole bag.
Also known as
TG we-Calculate Editorial Team. (2026). Grass Seed Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/grass-seed-calculator
TG we-Calculate Editorial Team. "Grass Seed Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/grass-seed-calculator.
TG we-Calculate Editorial Team, "Grass Seed Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/grass-seed-calculator
@misc{wecalculate_grass_seed_calculator, title = {Grass Seed Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/grass-seed-calculator}}, year = {2026}, note = {TG we-Calculate} }
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