Lawn Seed and Fertiliser Calculator
Work out how much grass seed and lawn fertiliser to buy for your lawn’s area, from the rate on the packet. Free, private and instant.
How to use the Lawn Seed and Fertiliser Calculator
- Enter your lawn’s area in square metres.
- Choose a new lawn or overseeding seed rate, or enter the rate from your seed packet.
- Enter the nitrogen you want to apply and the nitrogen percentage on the fertiliser bag.
- Read how much seed and fertiliser to buy, and how many boxes and bags.
Example
Worked example (100 m², new lawn, 3 g N per m² from a 12% fertiliser)
- Seed: 100 × 35 g = 3.5 kg, which is 4 boxes of 1 kg
- Fertiliser per m²: 3 ÷ 0.12 = 25 g
- Fertiliser for the lawn: 2.5 kg, which is 1 bag of 10 kg
Limitations
- The seed rates are typical, not universal. Follow the rate on your seed packet.
- Fertiliser rates depend on the season, the product and your lawn, so follow the label.
- The calculator does not allow for uneven spreading or for wasted product.
- Not agronomic advice.
Sources
About this tool
The Lawn Seed and Fertiliser Calculator turns the area of your lawn into the amount of grass seed and fertiliser to buy. The seed rate defaults to a typical figure for a new lawn or for overseeding, and the fertiliser amount comes from how much nitrogen you want to apply and the nitrogen percentage on the bag. Both rates are editable, because the packet’s own rate is the one to follow.
Also searched for as: how much grass seed do I need, lawn feed calculator, fertiliser per square metre, grass seed per square metre, overseeding calculator, nitrogen rate calculator.
Lawn Seed and Fertiliser Calculator is part of ToolStack Hub's Calculators. It runs entirely in your browser, which keeps your data private and makes results instant. There is nothing to install and no account to create. There is no usage limit.
Frequently asked questions
How much grass seed do I need per square metre?
Typically about 35 g per m² for a new lawn and about 20 g per m² for overseeding. Check the packet.
How do I work out how much fertiliser to use?
Divide the nitrogen you want to apply by the percentage of nitrogen in the bag. 3 g of N from a 12% bag is 25 g of fertiliser per m².
When should I sow grass seed?
Early autumn or spring are commonly recommended, when the soil is warm and moist.
Is the Lawn Seed and Fertiliser Calculator free?
Yes. Lawn Seed and Fertiliser Calculator is completely free with no sign-up, limits or watermarks.
Is my data private when I use the Lawn Seed and Fertiliser Calculator?
Yes. It runs in your browser, so your input is not uploaded to our servers.
Does it work on mobile?
Yes. ToolStack Hub tools work on phones, tablets and desktop browsers.
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