Grass Seed and Sod Calculator
How much grass seed, or how many rolls of sod, your lawn needs.
Good to know. More seed is not a thicker lawn. Crowded seedlings fight for light and water, and many lose.
How it works
In plain words
Seed: multiply the area by the rate on the bag, and halve the rate to overseed an existing lawn. Sod: divide the area, plus a little for cutting around edges, by the area of one roll and round up.
The formula
seed (kg) = area (m²) × rate (g/m²) ÷ 1,000 seed (lb) = area (sq ft) × rate (lb per 1,000 sq ft) ÷ 1,000 rolls = ⌈area × (1 + extra) ÷ roll area⌉
Worked example
A new 50 m² lawn at a typical 35 g/m² needs 50 × 35 = 1,750 g, so 1.75 kg of seed: two 1 kg bags. Overseeding the same lawn takes about half. As sod, it is 53 rolls of 1 m², with 5% for cutting.
Sources
No outside data or rates: this is plain arithmetic.
4 automated tests check its answers on every change.
About the grass seed and sod calculator
Seed bags print a sowing rate, the weight to spread over a given area, and it is the number to use: it depends on the grass. Fine-seeded grasses like Kentucky bluegrass need far less weight than big-seeded ones like ryegrass or tall fescue, because a pound holds many more seeds. Without a rate, the calculator uses 35 grams per square metre (about 7 lb per 1,000 sq ft), a common rate for new lawns of mixed grass.
Overseeding thickens a thin lawn without starting again, and takes about half the new-lawn rate. Mow short, rake out the thatch, sow, and keep the soil moist until the grass is up. Late summer and early autumn are usually best: the soil is warm and the weeds are fading.
Sod, or turf, gives an instant lawn at a higher price. Rolls are commonly 1 m² in Europe and 2 by 5 feet (10 sq ft) in the US, but check the supplier; pallets hold a few hundred square feet. Order about 5% extra for cutting around beds and curves, and lay it the day it arrives.
For an odd-shaped lawn, add up rectangles with the area calculator. For topsoil underneath, use the mulch, soil and gravel calculator.
Questions people ask
How much grass seed do I need?
Multiply the area by the rate on the bag. At 35 g/m², a 50 m² lawn needs 1.75 kg; at 7 lb per 1,000 sq ft, 1,000 sq ft needs 7 lb.
How much seed to overseed a lawn?
About half the rate for a new lawn, so roughly 15–20 g/m² or 3–4 lb per 1,000 sq ft.
How many rolls of sod do I need?
Divide the area by the area of one roll and add about 5%. 50 m² of 1 m² rolls is 53 rolls.