A seed label states the amount to spread on each unit of area. The purchase is that amount scaled to your lawn, then rounded up to whole bags. This page is about reading that arithmetic, from the label to the cart.
Seed weight = lawn area ÷ 1,000 sq ft × label rate (lb)
Bags = seed weight ÷ bag weight, rounded up
Supplied weight = bags × bag weight
A lawn of 5,500 sq ft
A label reads 4 lb per 1,000 sq ft and the bag is 10 lb. The lawn is 5,500 sq ft, so it is 5.5 thousand square feet. Then 22 lb of seed are needed, which is 2.2 bags before rounding. The list says 3 × 10 lb bags, which supplies 30 lb: the whole bags carry more than the calculated weight, and the extra is simply the rest of the last bag.
Worked example 5,500 sq ft lawn, label rate 4 lb per 1,000 sq ft (an example), 10 lb bags
| Material | Calculated | Buy |
|---|---|---|
| Grass seed4 lb / 1,000 sq ft label rate | 22 lb | 3 × 10 lb bags |
The same lawn in metric
In metric the rate is written in kilograms per 100 square meters. The label rate of 4 lb per 1,000 sq ft is 1.95 kg per 100 sq m, the 10 lb bag is 4.54 kg, and the lawn is 511 sq m. The weight scales by the same arithmetic: 9.98 kg needed, and the planner says 3 × 4.54 kg bags, the same number of bags as above. Imperial and metric come from one conversion table, so they cannot disagree.
A label that gives coverage, not a rate
If your label gives the area a bag covers instead of a rate, turn it into a rate first: the rate is the bag weight divided by its coverage, multiplied by 1,000. A 10 lb bag covering 2,500 sq ft is 4 lb per 1,000 sq ft, which is the rate to enter. If the label gives separate figures for a new lawn and for overseeding, use the one for your job.
This example assumes
- 4 lb per 1,000 sq ft, a 10 lb bag and a 5,500 sq ft lawn are examples, not recommended values
- The planner starts with no extra allowance
Check before you buy
Use the rate printed on the seed you are buying, and the bag weight printed on that bag. The planner does not know either, and it deliberately has no built-in rate. For why rates differ and how the whole purchase fits together, see how much grass seed you need. If you are weighing seed against turf, how much sod you need covers the other route.
What changes the estimate?
- The label rate, in lb per 1,000 sq ft or kg per 100 sq m
- The bag weight, in lb or kg
- Which use the label rate is for, such as a new lawn or overseeding
- The lawn area, including every separate section