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Last updated: October 3, 2026
Grass seed calculator
Work out grass seed for a new or patchy lawn. US units: feet, inches and cubic feet. Results update as you type.
How to use this calculator
Measure the lawn's length and width. Then enter the sowing rate printed on your seed pack. Rates differ a lot between grass types and between sowing a new lawn and overseeding.
How it's calculated
Seed = area × sowing rate (pounds per 1,000 square feet).
Worked example
A lawn 30 ft × 20 ft is 600 sq ft. At 5 lb per 1,000 sq ft you need 600 ÷ 1,000 × 5 = 3 lb of seed.
Common questions
What sowing rate should I use?
Use the rate on your seed pack. It depends on the grass type and whether you're starting a new lawn or thickening an existing one.
Is more seed better?
Not always. Sowing far too thickly can make seedlings compete and weaken. Stick close to the recommended rate.
When is the best time to sow?
Usually when the soil is warm and moist. The right months depend on where you live and the grass type.