# 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.

- URL: https://toolstackhub.co.uk/tools/lawn-seed-and-fertiliser-calculator/
- Category: Calculators
- Price: free, no sign-up
- Privacy: runs in the browser; input is not uploaded
- Last updated: 2026-10-08

## About
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.

## How to use
1. Enter your lawn’s area in square metres.
2. Choose a new lawn or overseeding seed rate, or enter the rate from your seed packet.
3. Enter the nitrogen you want to apply and the nitrogen percentage on the fertiliser bag.
4. Read how much seed and fertiliser to buy, and how many boxes and bags.

## FAQ
**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, with no sign-up or limits.