How much grass seed, starter fertilizer or sod your lawn needs

How the grass seed calculator works

Seed to buy is the lawn area times the seeding rate, divided by the bag weight and rounded up to whole bags. The rate is on the bag, written in the US as pounds per 1,000 sq ft: Pennington Kentucky 31 Tall Fescue asks for 12 lb per 1,000 sq ft on a new lawn and 5 lb for overseeding. If a bag only gives coverage, such as Scotts Rapid Grass at 615 sq ft per 5.6 lb bag, enter 5.6 lb per 615 sq ft and the calculator does the division. Seed and fertilizer each have their own area field, so changing one leaves the other alone.

A new lawn and overseeding have separate fields because an existing lawn needs less seed. Starter fertilizer works the same way with its own rate: Scotts Starter Food for New Grass covers 5,000 sq ft with a 15 lb bag, which is 3 lb per 1,000 sq ft. Set the fertilizer rate to zero and it drops off the receipt.

For sod, the count is area × (1 + extra for cuts) ÷ the area of one roll, rounded up. The default extra is 5%, the low end of the 5 to 10% that Sod Solutions recommends. If your sod farm sells by the pallet, the receipt splits the order into full pallets and loose rolls.

A worked example

In feet (US). The calculator opens with a 40 × 25 ft lawn.

• Area: 1,000 sq ft
• New lawn at 12 lb per 1,000 sq ft: 12 lb of grass seed, 2 bags of 7 lb
• Starter fertilizer at 3 lb per 1,000 sq ft: 3 lb, 1 bag of 15 lb
• Overseeding at 5 lb per 1,000 sq ft: 5 lb of seed, 1 bag of 7 lb
• Sod: 1,000 sq ft plus 5% is 1,050 sq ft, or 105 sod rolls of 2 × 5 ft: 2 pallets of 50 rolls and 5 loose rolls, or 3 full pallets

In metres (UK and elsewhere). A 10 × 8 m lawn is 80 m². At 25 g/m² it takes 2 kg of lawn seed, 2 packs of 1 kg, and 2 kg of pre-seed fertiliser at 25 g/m². Overseeding at 20 g/m² takes 1.6 kg. Turf in 1 m² rolls comes to 84 rolls with 5% extra.

Seeding rates for new lawns and overseeding

Product	New lawn	Overseeding	Source
Pennington Kentucky 31 Tall Fescue	12 lb / 1,000 sq ft	5 lb / 1,000 sq ft	Pennington
Pennington The Rebels Tall Fescue	8-10 lb / 1,000 sq ft	4-6 lb / 1,000 sq ft	Pennington
Scotts Rapid Grass Tall Fescue Mix	about 9 lb / 1,000 sq ft	about 3 lb / 1,000 sq ft	Scotts, 5.6 lb bag
Sports lawn seed (Europe)	25 g/m²		Hauert
COMPO Turbo-Nachsaat (Europe)		20 g/m²	COMPO

The Scotts figures come from the bag coverage: 5.6 lb over 615 sq ft and over 1,845 sq ft. Rates change with the grass type and the brand, so the bag you buy has the final word. In metric, 1 lb per 1,000 sq ft is about 4.9 g/m².

Buying seed bags, fertilizer and sod pallets

Grass seed comes in bags of several sizes: Pennington sells Kentucky 31 in 3, 7, 20 and 40 lb bags. A 7 lb bag of Kentucky 31 covers up to 1,400 sq ft when overseeding, so change the bag size in the calculator and the count follows while the pounds stay the same. Scotts Starter Food comes in a 15 lb bag for 5,000 sq ft.

Sod is cut in rolls or slabs. Sod Solutions lists large rolls of 60 × 24 in or 80 × 18 in at 10 sq ft each, on pallets of 500, 600 or 700 sq ft, and smaller slabs of 16 × 24 in. The calculator opens with 2 × 5 ft rolls and 50 rolls per pallet; check both numbers with your sod farm. In Europe turf is ordered by the square metre: Hornbach's rolls are 250 × 40 cm, 1 m² each.

Common mistakes

• Using the new lawn rate for overseeding. An existing lawn needs less: 5 lb instead of 12 lb per 1,000 sq ft on Kentucky 31.
• Reading coverage as a rate. "Covers 615 sq ft" is for the whole bag: enter the bag weight over that area, not per 1,000 sq ft.
• Ordering sod without extra. Curved edges, beds and paths all need cuts: Sod Solutions advises 5 to 10% more.
• Lining up the roll ends. The Swiss seed company Eric Schweizer tells you to stagger the joints and butt the edges tight, because the rolls shrink a little after laying.
• Leaving sod on the pallet. Lay it the day it arrives, keep it in the shade and never water it on the pallet.