GardenCalc

Lawn Feed Calculator

Work out exactly how much lawn feed you need per square metre. No scorched patches, no wasted product.

Calculate Your Lawn Feed

Choose your lawn feed type, enter your lawn dimensions — we'll tell you exactly how much to apply and how many packs to buy.

Your Results

Lawn Area
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Feed Needed
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Weight
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Packs Needed
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How Much Lawn Feed Do I Need?

This free lawn feed calculator tells you exactly how much feed your lawn needs based on its size and the product you're using. Select from popular UK lawn feed types — spring/summer, autumn/winter, weed & feed, moss killer — or enter a custom rate. Get results in grams, kilograms and pack counts instantly.

Getting the amount right matters. Too little and you won't see results. Too much and you'll scorch your lawn with brown patches that take weeks to recover.

Lawn Feed Application Rates

Different products need different rates. Use this guide with the calculator above.

Product Rate (g/m²) When to Apply Notes
Spring/summer feed35Mar–SepHigh nitrogen for green growth
Autumn/winter feed70Sep–NovHigh potassium, strengthens roots
Weed & feed50Apr–SepFeeds grass + kills broadleaf weeds
Moss killer feed35Mar–Apr, Sep–OctContains ferrous sulphate
Iron sulphate4Any seasonDissolve in water, 4g per 1L per m²
Liquid concentrate50 mlMar–Sep50ml per 10L water covers 10m²

How to Apply Lawn Feed Evenly

Using a spreader

A wheeled or handheld spreader gives the most even coverage. Set the aperture to the product's recommended setting. Walk at a steady pace, overlapping each pass by about 10cm. Apply half the product north-to-south, then the other half east-to-west for the most uniform result.

Applying by hand

If you don't have a spreader, divide your total feed into equal portions — one per strip of lawn about 1 metre wide. Scatter each portion evenly as you walk the strip. A level adult handful of granular feed is roughly 35–40g, which covers about 1 square metre at standard rate.

After applying

Water in thoroughly if rain isn't expected within 48 hours. Keep children and pets off the lawn until the feed has been watered in and the grass is dry. Don't mow for at least 3 days after feeding to give the product time to work.

Frequently Asked Questions

How much lawn feed do I need per square metre?
Most granular lawn feeds are applied at 35g/m², but it varies by product. Spring/summer feeds are typically 35g/m², autumn feeds around 70g/m², and weed & feed products range from 35–50g/m². Always check the pack instructions and use the calculator above for your exact area.
How do I measure my lawn size?
For rectangular lawns, multiply length by width. For L-shaped lawns, split into two rectangles and add the areas. For irregular shapes, use the irregular option in the calculator and estimate total area. One adult pace is roughly 0.75m if you need to step out the dimensions.
When should I feed my lawn in the UK?
Feed 3–4 times per year: first in March/April with a high-nitrogen spring feed, again in June and August, then a final autumn feed (high potassium, low nitrogen) in September/October. Avoid feeding in winter, during drought, or on frozen/waterlogged ground.
What happens if I put too much lawn feed on?
Over-feeding causes 'fertiliser burn' — brown or yellow patches from excess nitrogen salts. It also promotes lush, weak growth vulnerable to disease. If you over-apply, water the area heavily immediately to dilute. Always measure your lawn and use the correct rate to avoid this.