Lawn Seed Calculator
Estimate grass seed weight, bag count, coverage, and cost for a new lawn or overseeding job. Pick your grass type, enter one or more lawn zones, and the seeding rate updates automatically.
Lawn zones
Deep-rooted, durable, and a common all-round family lawn pick.
Grass seed rate guide
3 lb / 1,000 ft²
1.46 kg / 100 m²
6 lb / 1,000 ft²
2.93 kg / 100 m²
8 lb / 1,000 ft²
3.91 kg / 100 m²
1.5 lb / 1,000 ft²
0.73 kg / 100 m²
0.5 lb / 1,000 ft²
0.24 kg / 100 m²
About the Lawn Seed Calculator
The Lawn Seed Calculator helps you work out exactly how much grass seed to buy before you start a new lawn or overseeding project. Enter one or more lawn zones, choose the grass type, and switch between new lawn and overseed mode. The calculator totals the area, applies your selected seeding rate, adds a small allowance, and returns the final seed weight in pounds and kilograms.
Each grass preset has its own real seeding rate because turf species behave differently. Kentucky bluegrass needs a lighter application than tall fescue or perennial ryegrass, while warm-season grasses like Bermuda and centipede are much lighter again. Picking the right preset matters more than most DIY users expect.
Use the bag size and price inputs to convert the seed weight into a practical shopping list. That lets you see how many bags to buy, roughly how much each bag covers at your chosen rate, and the likely total spend before you head to the garden centre.
How to Use the Lawn Seed Calculator
- 1 Pick imperial or metric. The calculator supports feet or metres for each lawn zone without changing the seeding logic.
- 2 Choose the grass type. Each preset loads a realistic new-lawn seed rate so you do not have to guess from a product label.
- 3 Set new lawn or overseed. Overseeding uses half the new-lawn rate because existing turf still covers part of the ground.
- 4 Add each lawn zone. Rectangles cover most gardens, but circular patches and tree-surround lawns can be entered too.
- 5 Set allowance, bag size, and price. A small allowance helps with borders, missed spots, and future touch-up patches.
- 6 Buy the rounded-up bag count. The result is rounded to whole bags so you do not run short halfway through spreading.
Frequently Asked Questions
What is the difference between new lawn and overseeding? ▾
A new lawn starts from bare soil, so you use the full seed rate. Overseeding means you already have grass and just want to thicken weak areas, so you normally use about half as much seed.
How much area does one bag of grass seed cover? ▾
It depends entirely on the bag weight and the seed rate. A heavier-seeded grass like tall fescue covers less area per bag than Bermuda. This calculator shows the coverage of your chosen bag size at the exact preset rate you selected.
Why do different grass types need different seed rates? ▾
Seed size, turf density, and how the grass spreads all affect the recommended rate. Kentucky bluegrass seeds are smaller and are often applied lighter, while tall fescue and perennial ryegrass are seeded more heavily to establish a dense lawn quickly.
When is the best time to seed a lawn? ▾
Cool-season grasses like Kentucky bluegrass, perennial ryegrass, and tall fescue are usually best seeded in early autumn or spring. Warm-season grasses like Bermuda and centipede are usually seeded in late spring to early summer once the soil is warm.
Should I buy extra seed? ▾
Usually yes. Keeping a small amount back for thin edges, bird loss, or a quick patch a few weeks later is sensible. That is why the calculator includes an allowance field with 5% as the default.
Is my data saved or sent anywhere? ▾
No. The calculator runs entirely in your browser. Lawn dimensions, prices, and seed choices stay on your device and are not sent to a server.