Lawn Overseeding & Seed-Rate Calculator
A thin, patchy lawn can often be revived without starting from scratch, and overseeding is how you do it. This Lawn Overseeding and Seed-Rate Calculator works out how much grass seed you need to thicken an existing lawn at the right rate, so you fill the gaps without wasting seed or smothering the grass you already have. It uses metric measurements and Australian lawn-care conditions, turning your lawn area and chosen seed rate into a clear quantity. Enter your details below to get your seed amount.
Lawn Overseeding & Seed‑Rate Calculator
Work out exactly how much grass seed you need for overseeding or a full lawn renovation.
Result
How this calculator works
The calculator multiplies your lawn area by the seeding rate for your grass type, which gives the total amount of seed to buy and spread. Overseeding uses a lighter rate than establishing a brand-new lawn, because the existing grass already covers much of the ground. The tool lets you choose or enter the rate so you can match the seed and the job. The result is a practical quantity to take to the store, along with a sense of how many bags you need for larger areas.
Quick tip Mow low and rake or scarify the lawn before you sow, so the seed reaches the soil rather than sitting on top of the thatch. Then keep the surface consistently moist until the new grass is up.
What you need before using it
- Your lawn area in square metres — measure length by width, or add up separate sections.
- The grass seed type and its recommended seeding rate.
- Whether you are overseeding a thin lawn or establishing bare ground, as the rate differs.
- The bag size, if you want to know how many bags to buy.
Practical Australian guidance
Overseeding timing depends on whether you are using cool-season or warm-season grass seed, your local climate and soil temperature, so check the seed supplier guidance before sowing rather than assuming all Australian lawns should be overseeded at the same time. Cool-season grasses like ryegrass and fescue establish best as the weather cools, while warm-season lawns prefer the warmth of late spring and summer. Prepare the surface by mowing low and loosening the thatch, sow evenly, and keep the seed moist through germination. Choose a seed blend suited to your region, sun and wear, and be patient, as new grass takes a few weeks to thicken up.
Common mistakes to avoid
- Sowing too heavily, so seedlings compete and thin themselves out.
- Using the wrong seed for the season, so germination is poor.
- Letting the seed or seedlings dry out during germination.
- Sowing onto an unprepared, thatchy surface so seed never reaches the soil.
Related calculators
Lawn Size & Turf Quantity Calculator
Lawn area and turf rolls needed, with a waste allowance.
Top-Dress Volume & Blend Calculator
Top-dressing soil or sand blend to level your lawn.
Frequently Asked Questions
Multiply your lawn area by the overseeding rate for your grass type. The calculator does this for you and can also estimate how many bags you need for larger lawns.
Overseeding uses a lighter rate than a new lawn because existing grass already covers the ground. Follow the rate on your seed label for overseeding, and enter it into the calculator for your area.
It depends on your grass. Cool-season grasses establish best as the weather cools, while warm-season lawns prefer late spring and summer. Check your seed supplier guidance for local timing.
Warm-season lawns like couch and kikuyu are usually thickened by encouraging their runners in the warm months, and some people oversow a temporary cool-season grass for winter colour. Follow the seed guidance for your lawn type.
Yes. Enter your area in square metres and the seeding rate in metric. If you have imperial figures, convert them first.
Please note These seed quantities are planning estimates based on your area and chosen rate. Actual results vary with grass type, seed quality, soil preparation, weather and watering, so treat the figure as a starting point and follow the seed supplier directions for the best result.
