Lawn Fertiliser Calculator UK | How Much Fertiliser Do I Need?
UK Lawn Fertiliser Tool

Lawn Fertiliser
Calculator UK

Work out exactly how many kilograms of lawn feed you need from the label rate in g/m² — for spring, summer and autumn fertilisers.[web:21][web:24][web:18]

Spring Green-up Summer Growth Autumn Root Strength
Calculate Fertiliser NPK Guide
Tool

Lawn Fertiliser Quantity Calculator

Application rates for granular lawn fertilisers are usually between 25–35 g/m². Always copy the exact rate from your product label, then use this calculator to find the total quantity needed.[web:21][web:24][web:18]

Granular Fertiliser Calculator

For spring, summer and autumn lawn feeds (solid granules)

If you enter length AND width, area is calculated automatically.[web:21]
Most UK granular lawn feeds are applied at 25–35 g/m²; some premium products allow up to 40 g/m².[web:21][web:42][web:41][web:46][web:43]
Add a bag price to estimate the total cost of fertilising your lawn.[web:18]
Fertiliser Required
Area
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m²
Rate
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g/m²
Total Product
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g
Total Kilos
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kg
Chosen bag size
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10 kg bags
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20 kg bags
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Estimated Cost (optional)
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NPK & Rates

Typical UK Lawn Fertiliser Ratios & Application Rates

These examples mirror common UK lawn fertilisers, their NPK ratios and typical label rates in g/m².[web:21][web:41][web:42][web:43][web:46][web:36]

Season Example NPK Use Typical Rate (g/m²) 20 kg Bag Coverage (m²)
Spring 10–4–4 High N spring green-up[web:21][web:46] 30–35 ≈ 570–667[web:42][web:46]
Spring / Summer 9–7–7 General growth & colour[web:21] 25–35 ≈ 571–800[web:42]
Pre-seed 6–9–6 Before seeding new lawn[web:21] 25–35 ≈ 571–800
Autumn 3–12–12 Root strength & winter prep[web:21][web:41][web:43] 25–40 ≈ 500–800
Autumn + Fe 6–5–10 + Fe Hardening off, moss help[web:21] 25–35 ≈ 571–800

Swipe sideways to see the full table on small screens.

UK Styles

Example UK Lawn Fertiliser Types

These mirror common product types: spring boost, summer maintenance and autumn hardener.[web:21][web:41][web:42][web:43][web:46]

Spring

Spring / Summer High-N Feed

Typical NPK10–4–4 or 9–7–7
UseMarch–June green-up
Rate25–35 g/m²

Higher nitrogen drives leaf growth and colour in the main growing season.[web:21][web:42][web:46]

MOST USED
All Season

Balanced Slow-Release

Typical NPK18–3.5–8 + Mg
UsePhased release growth
Rate25–35 g/m²

Phased-release fertilisers maintain colour and growth while lowering scorch risk.[web:21]

Autumn

Low-N Autumn / Winter Feed

Typical NPK3–12–12 or 6–5–10 + Fe
UseAug–Oct root hardening
Rate25–40 g/m²

Low nitrogen, high potassium to toughen turf before winter and help resist disease.[web:21][web:41][web:43]

NPK Guide

How to Choose the Right Lawn Fertiliser

Match NPK and rate to the season and what you want from the lawn — growth, colour, or winter strength.[web:21][web:34][web:24]

Understanding NPK ratios

The three big numbers on a fertiliser bag are nitrogen (N), phosphorus (P) and potassium (K). High‑N spring/summer feeds (e.g. 10–4–4) push leaf growth and colour, while low‑N, high‑K autumn feeds (e.g. 3–12–12) focus on roots and disease resistance.[web:21]

Why application rate matters

Every fertiliser bag shows a recommended rate, usually 25–35 g/m² for lawn granules.[web:21][web:24] Using less gives weak results; using more risks scorch and excess nutrients. The simple formula is: quantity needed = rate (g/m²) × area (m²).[web:21][web:18][web:34]

Seasonal strategy

  • Spring: Higher nitrogen for green-up as growth restarts.[web:21][web:46]
  • Summer: Maintain colour with balanced or phased-release feeds.[web:21]
  • Autumn: Low nitrogen, higher potassium to harden the turf for winter.[web:21][web:41][web:43]
  • Winter: Use specialist autumn/winter products only; avoid standard high‑N feeds.[web:21][web:24]

Example: 200 m² Spring Feed

Assume a 200 m² lawn and a spring fertiliser label rate of 30 g/m² (within the 25–35 g/m² band):[web:21][web:42][web:46]

  • • Quantity needed = 200 × 30 g = 6,000 g
  • • 6,000 g = 6.0 kg total fertiliser
  • • One 10 kg bag easily covers the job, leaving some spare for edges

At the same rate, a 20 kg bag would cover roughly 666 m² of lawn, matching the coverage shown on many UK spring fertiliser labels.[web:42][web:46][web:36]

FAQ

Lawn Fertiliser — Frequently Asked Questions

Quick answers on rates, timing and how to avoid scorching a UK lawn.[web:21][web:24][web:45][web:18]

Most granular lawn fertilisers are applied at 25–35 g/m², but the exact rate is always printed on the product label.[web:21][web:24][web:18] Premium products may have a wider band, such as 25–40 g/m², to suit different lawn conditions.[web:41][web:42][web:43][web:46]
Multiply your lawn area in m² by the label rate in g/m² to get the total grams required, then divide by 1,000 to convert to kilograms.[web:21][web:18][web:34] The calculator at the top of this page does this for you automatically.
For spring green‑up, a high‑nitrogen product such as 10–4–4 or 9–7–7 is commonly recommended to promote strong leaf growth and colour.[web:21][web:46][web:42] Apply from March to June when grass is actively growing.
In autumn, use a low‑nitrogen, higher‑potassium feed such as 3–12–12 or 6–5–10 + iron.[web:21][web:41][web:43] This strengthens roots and helps the lawn resist disease and winter stress rather than pushing soft growth.
You can, but it is not ideal. High‑nitrogen spring feeds are unsuitable for autumn/winter, and autumn feeds are too low in nitrogen for strong spring growth.[web:21][web:24] Using season‑specific products gives better results and reduces disease risk.
Never exceed the label rate, spread as evenly as possible with a calibrated spreader, and apply just before or during light rain so granules wash into the soil.[web:21][web:45] Avoid applying in very hot, dry conditions or onto frosted turf.

Ready to feed your lawn properly?

Use the calculator to size your application, then follow the NPK and seasonal guide so you feed at the right rate and time of year.

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