Bare soil, a thin existing lawn and a handful of damaged patches are three different starting points. Identify the job first, then use the seed rate printed for that job on your chosen mix.
When you are sowing from bare soil, the whole area has to support germination and establishment. RHS recommends preparing the soil, choosing a seed mix suited to the site, weighing the correct quantity for the lawn area and sowing it evenly. One practical technique is to split the seed into two batches and sow in crossing directions so distribution is more even.
For the quantity, calculate the actual lawn area and use the new-lawn rate printed on your product. The Grass Seed Calculator converts that rate into grams, kilograms and whole packs.
Overseeding means introducing fresh seed into grass that is already there. The challenge is therefore different: new seed has to reach the soil surface instead of sitting on thatch or dense foliage. Current UK supplier guidance commonly recommends mowing and removing clippings before overseeding, and improving seed-to-soil contact by raking or scarifying where needed.
Do not assume the new-lawn rate applies. Use the overseeding rate supplied for your mix. A current Johnsons general-purpose lawn seed example lists 35 g/m² for a new lawn and 20 g/m² for overseeding; other products can differ, which is why the calculator leaves the rate editable.
If the rest of the lawn is healthy, measure only the damaged sections. RHS guidance describes reseeding bare patches as a repair option, but also notes that a lawn in very poor condition may justify complete reseeding or returfing rather than repeated patch work.
The contents of lawn-seed mixes vary, and so can the recommended application rate. Seed size, species mix, coating and intended use all affect coverage. The reliable workflow is therefore:
RHS guidance identifies early autumn and mid-spring as good times to establish a new lawn from seed because the soil is warm and moisture is usually available. It likewise recommends spring or autumn for lawn repairs. Local conditions still matter: seed needs suitable soil temperature and moisture, and sowing into drought, waterlogging or unsuitable soil can undermine the job regardless of the calendar.
RHS advises watering newly sown seed gently when rain is not expected and keeping young grass from drying out while it establishes. Avoid washing seed into piles. For a new lawn, first mowing should wait until the seedlings are established enough to take a light cut; follow the seed supplier's instructions and keep early mowing conservative.
Overseeded lawns already contain established grass, but the new seedlings still need moisture and time to root. Heavy wear immediately after sowing can work against that establishment.
The new-lawn timing and sowing principles in this guide are based on current RHS advice on starting lawns from seed. Repair guidance is cross-checked against RHS lawn-repair advice. A current Johnsons Lawn Seed product guide provides a real-world example of different new-lawn and overseeding rates, but your own product label remains the correct rate to enter.
Enter the measured lawn area and your seed pack's matching g/m² rate.
Compare seed with turf quantities and ground preparation before deciding.