Understanding your result
The base weight follows the label rate exactly. The adjusted weight includes your optional allowance, while purchased weight and cost reflect whole bags. These are different quantities and should not be confused when setting the spreader.
If your soil-test guidance also specifies nitrogen, the Fertilizer Application Calculator converts that target into product weight.
The formula
Grams per square metre multiplied by square metres gives grams of product. Converting to kilograms makes the requirement comparable with the package size. A purchase allowance is additional stock; it does not automatically increase the recommended application rate.
Worked example
A 250 m² lawn at 30 g/m² needs 7.5 kg. With 5% extra stock, plan for 7.875 kg. Two 5 kg bags provide 10 kg, costing 70 if each bag costs 35.
How to use this calculator
- Measure the lawn and subtract paths, beds, and other unseeded areas.
- Read the product rate for new establishment or overseeding.
- Enter package weight, price, and any spare-stock allowance.
New lawns and overseeding
The appropriate rate depends on the seed mixture and the job. A bare seedbed and an existing lawn with thin patches need not use the same rate. The default value is an arithmetic example, not a recommendation for every species. Use the specific product label or a locally appropriate extension recommendation.
Product weight versus viable seed
Coated products and mixtures can include material other than viable grass seed. If a recommendation is expressed as pure live seed rather than total bag weight, it must first be converted using the product purity and germination information. This calculator assumes the rate you enter already refers to the bagged product being purchased. It does not perform that conversion or select a spreader setting.
Assumptions & limitations
What this calculation assumes
- The entered rate describes the exact product in the bag.
What to keep in mind
- Uneven ground, seed loss, germination and spreader calibration are not predicted.
Common questions
Should I spread the allowance as well?
Not automatically. Extra purchased stock can cover gaps or later touch-ups; apply according to the appropriate label rate.
Can I calculate several lawn sections?
Yes. Add the areas if they use the same mixture and rate. Different seed products should be calculated separately.