How much grass seed do I need?

Convert measured lawn area and the selected packet’s sowing rate into seed kilograms and whole bags.

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ToolLawn Seed Calculator
Input
Output
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How it works

Square metres are multiplied by grams per square metre, converted to kilograms, and divided by the selected bag weight. Any fractional bag rounds upward, while no generic new-lawn or overseeding rate is inserted.

Formula
seed grams = area m² × packet rate g/m²
  • RHS says to follow the packet rate and gives 15–25 g/m² only as a usual repair range.
  • Area, label rate, and bag size are therefore all required.

Worked example

A 50 square metre new lawn
Bags sold at 1kg
Input
											Area m2: 50
Seed rate gper m2: 35
Bag size kg: 1
Output
												Seed needed g: 1750
Seed needed kg: 1.75
Rate used gper m2: 35
Bags needed: 2

When to use this

Bare-soil establishment uses the packet’s new-lawn rate, patch repair uses its repair rate, and retail ordering converts the resulting kilograms into the chosen pack size.

Edge cases

  • A packet’s new-lawn rate may differ from its overseeding rate; enter the rate for the actual operation rather than reusing one number.
  • An irregular lawn measured as its bounding rectangle includes paths and beds; total only the rectangles or measured area that will receive seed.
  • A 1.75 kg requirement in 1 kg packs rounds to two whole bags, leaving 0.25 kg after sowing at the entered rate.

References