Seed Coverage Calculator

Grass seed, cover crops, wildflower mixes, and broadcast vegetables are sold with an application rate on the label — pounds or kilograms per unit area, or grams per square meter. Total seed needed equals planted area multiplied by that rate. This calculator handles the multiplication so you buy the right number of bags before overseeding a lawn or filling a new bed.

Rates vary by species, cultivar, germination percentage, and whether you are establishing new turf or thickening thin patches. New lawn seeding often uses higher rates than overseeding into existing grass. Cover crop mixes list separate rates per species — use the blended rate on your bag unless you are custom mixing.

Convert common US label units before entering the rate field. A packet that says 4 lb per 1,000 sq ft equals 0.004 lb per sq ft (divide by 1,000). Metric labels may already state grams per m², which you can enter directly when the unit toggle is set to metric.

Buy extra for uneven spreading, wind loss, and bird theft — a 10% buffer is common for hand broadcasting; drop spreaders often waste less. Stored seed loses viability over years; check the pack date and germination test if you are using old inventory.

Drill seeding and row planting use seed counts per foot, not area rates — this tool is for broadcast and turf math. Transplants skip seed quantity entirely. For large acreage, confirm rates with your agricultural extension office because field crops use different units than home lawn bags.

Overseeding too densely invites fungus and competition; too thinly leaves bare patches. Split your calculated total in half if the label gives separate rates for new versus repair jobs. Water and soil prep matter as much as arithmetic for germination success. Rake seed into shallow contact with soil — broadcast seed sitting on thatch may never sprout regardless of quantity purchased.

Cool-season and warm-season grasses use different bag rates; confirm the species on the label matches your climate zone before multiplying area by rate. Mixing species without adjusting rates can over-seed one variety and under-seed another.

Worked example with default inputs: 2,000 sq ft of lawn at 0.004 lb per sq ft (equivalent to 4 lb per 1,000 sq ft) requires 8 lb of seed. In metric mode, 100 m² at 50 g/m² would need 5 kg — always match the rate unit to the area unit shown on your toggle.