Grass Seed and Fertilizer Calculator
Size a seeding job from lawn area alone: kilograms of grass seed at the right rate for overseeding or a new lawn, plus starter fertilizer amounts.
Your results
Worked example
A new lawn covers 500 m² and is seeded at the standard new lawn rate of 2.0 kg per 100 m²:
- Seed: 500 ÷ 100 × 2.0 kg = 10.0 kg of seed
- Fertilizer: 500 ÷ 100 × 2.5 kg = 12.5 kg
- Bags: 12.5 kg ÷ 10 kg per bag = 1.25, so 2 bags
The fertilizer figure uses the labelled assumption below, 2.5 kg per 100 m², which matches a typical 10 kg bag covering about 400 m². Starter fertilizer goes down at seeding; regular lawn fertilizer follows the rate on its own bag.
How this calculator works
Grass seed rates are stated per 100 m² because that is how Canadian seed guidance and most bag labels express them. Overseeding an existing lawn needs less seed per area than bare soil, and heavy rates suit fast cover on new lawns. The fertilizer rate here is a planning assumption for a typical granular product, stated openly: products vary, and the rate printed on the fertilizer bag always overrides this page.
Common questions
When is the best time to seed in Canada?
Late summer into early fall is the strongest window in most of the country: warm soil, cool nights, and fewer weeds. Spring seeding works but competes with crabgrass and summer heat arriving before roots establish.
Should I split the seed into two passes?
Yes. Apply half the seed walking one direction and half walking at right angles to it. Two lighter passes cover far more evenly than one heavy pass, for the same total kilograms.
Estimates only. Results are provided for planning purposes and use the seeding rates and the labelled fertilizer assumption shown on this page. Follow the rates on your seed and fertilizer product labels where they differ. Mississippi Maple accepts no liability for purchase decisions made using this calculator.