Lawn calculator
Enter the size of your lawn to get its area and the amount of seed, sod and fertilizer to buy. The rates are editable defaults, so check the label of your product.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose your units and enter the lawn length and width.
- Check the seed rate and the nitrogen target against your product labels.
- Read the amounts of seed, fertilizer and sod.
How it works
Area = length × width. Seed = rate × area. Fertilizer = nitrogen rate × area ÷ nitrogen share. Sod = area × (1 + waste ÷ 100).
Worked example
A 15 × 10 m lawn is 150 m². Seed at 25 g/m² is 3.75 kg. To apply 5 g of nitrogen per m² with a 20% product you need 750 g ÷ 0.20 = 3.75 kg of fertilizer. Sod with 10% waste: 165 m².
Tips
- The defaults are generic. Rates differ by species, season and product.
- Apply fertilizer with a spreader set as the label directs, never by hand-broadcasting a full dose.
Frequently asked questions
What seed rate should I use?
It depends on the grass species and on whether you are seeding a new lawn or overseeding. The default of 5 lb per 1,000 ft² (about 25 g/m²) is only a starting point: read the bag, then enter its rate.
How is the fertilizer amount worked out?
The nitrogen you want to apply per area, times the area, divided by the share of nitrogen in the product (the first number of the N-P-K label). 20% nitrogen means 5 lb of product per 1 lb of nitrogen.
Why order extra sod?
Cutting around curves, paths and beds wastes some pieces. 5–10% extra is the usual allowance.
How do I measure an irregular lawn?
Split it into rectangles and triangles, add their areas, then enter a length and width whose product matches the total.