Grass Seed Calculator
Calculate the exact quantity of grass seed needed for a new lawn or overseeding thin and bare patches. Based on standard UK seeding rates.
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Lawn Seeding Guide
What should I know about Seeding Rates?
Standard UK grass seed application rates: new lawn from seed 35-50g per m². Overseeding thin areas: 25-35g per m². Full renovation (after scarification): 35-50g per m². These rates are higher than many packet instructions because UK conditions (rain, slugs, birds) reduce germination success rate compared to ideal laboratory conditions. Always apply at the higher end of the recommended range for new lawns — thin germination is the most common new lawn problem and adding more seed is much cheaper
What should I know about Soil Preparation?
Soil preparation is the most important factor in successful lawn establishment. New lawns: remove all weeds (glyphosate-based weedkiller, then 2 weeks wait), rotovate to 15-20cm, remove stones and debris, firm with a roller or trampling (aiming for a fine, level tilth), rake to a fine surface. Overseeding: mow closely (3-4cm), scarify or rake vigorously to create soil contact, apply seed, top dress with a thin layer (5-10mm) of lawn dressing or compost to improve seed-soil contact. Seed contact with soil is the single biggest factor in germination success — seed left sitting on top of undisturbed ground or thatch will dry out and fail to establish.
What should I know about Timing and Germination?
Best sowing times in the UK: mid-August to mid-October (preferred) — soil is still warm from summer, autumn rains provide moisture without the need for constant irrigation, and competition from weeds is lower. March to May (second option) — soil warming from winter, but spring weeds compete. Avoid sowing in summer (drought risk without irrigation) or December to February (cold soil prevents germination). Germination time: 7-14 days in ideal conditions (15-25°C soil temperature, consistent moisture — allowing the seedbed to dry out during this window is one of the most common reasons new grass seed fails to establish.
What should I know about Lawn Care After Seeding?
Water daily in dry conditions until germination, then every 2-3 days as the lawn establishes (about 6 weeks). Do not let the seed dry out during germination — a 10-minute dry period during the germination stage can kill emerging seedlings. First feed: apply a pre-seeding fertiliser before sowing (high phosphorus to encourage root development) or a spring lawn feed 4-6 weeks after germination. Birds can be a significant problem — use a flutter tape or decoy predator over the seeded area for the first couple of weeks until the grass is established enough that birds pulling at emerging shoots is less of a concern.