Free Online Calculators
Calculate fertiliser amount for your lawn
This calculator works out exactly how much fertiliser you need for your lawn based on your lawn area and target nitrogen rate. It uses the nutrient content of your chosen fertiliser alongside the square footage to give you a precise application amount. No more guesswork – just a healthy, even lawn.
Measure your lawn's area, then work out how much nitrogen the grass should get over that area and divide by the nitrogen percentage shown on the bag. The result is the weight of product to spread; splitting it into two passes at right angles gives more even coverage.
Follow the application rate printed on the bag for your lawn's size, since the right amount depends entirely on the nitrogen content of that particular product. More is not better — excess nitrogen burns the blades, encourages disease and leaches into groundwater.
That depends on the analysis on the bag: a low-nitrogen organic product needs far more weight per given area than a concentrated synthetic one to deliver the same nutrients. Read the nitrogen percentage and calculate backwards from the nitrogen rate you want.
Price it from your material cost plus labour time and travel, then add your margin — lawn care rates vary widely by region and by whether it's a one-off or part of a season contract. Check what local competitors quote for a comparable property before setting your figure.
The coverage is printed on the bag and varies with the product's nutrient concentration, so two bags of the same weight can cover very different areas. Always use the manufacturer's stated coverage rather than assuming a standard figure.
It works, but it's not ideal for established lawns: grass mainly needs nitrogen, and a balanced blend supplies more phosphorus than most established turf can use. Balanced products suit new seedings or soils that a test has shown to be short on phosphorus and potassium.
It's the old farming name for a late spring snowfall, which was believed to feed the soil as it melted. The effect is modest — snow carries small amounts of nitrogen from the atmosphere and the slow melt puts moisture into the ground.
Neither is inherently better; they are the same balanced ratio at different strengths, so the more concentrated one simply needs less product per area. Choose based on what your soil test calls for and what's cheaper per unit of nutrient.
There isn't one — the best choice depends on your grass type, soil test results and the season. A slow-release nitrogen product suits most established lawns, while new seedings and nutrient-deficient soils need something matched to the deficiency.
A lush, green lawn doesn't happen by accident. It takes the right care, the right timing, and crucially, the right amount of fertiliser. Apply too little and your grass stays thin and patchy. Apply too much and you risk burning your lawn or creating an environmental hazard. Our free Lawn Fertiliser Calculator takes the guesswork out of the equation, helping you work out exactly how much fertiliser your lawn needs based on its size and the product you're using.
Fertilising your lawn is one of the most effective ways to promote healthy growth, improve colour, and strengthen the turf against weeds and disease. But the benefits only come when you apply fertiliser correctly. Here's why accuracy matters:
Using the calculator is straightforward. You don't need any specialist knowledge – just a few basic measurements and the details from your fertiliser packaging.
It's that simple. No complex maths, no unit conversions to wrestle with – just a clear, accurate answer in seconds.
Walk into any garden centre and you'll find shelves packed with different fertiliser products. The key to choosing the right one lies in understanding the NPK ratio – the three numbers printed on every bag representing Nitrogen (N), Phosphorus (P), and Potassium (K).
Seasonal lawn fertilisers are formulated with these needs in mind. A spring feed might be labelled 20-5-10, while an autumn product could read 5-5-20. Always match your fertiliser choice to the time of year and your lawn's specific needs.
Timing is just as important as quantity. Fertilising at the wrong time of year can do more harm than good.
Always check the weather forecast before applying. Fertiliser should be applied to moist soil but not before heavy rain, which can wash it away before absorption.
Even with the perfect quantity calculated, uneven spreading leads to patchy results. Here are some practical tips for a professional finish:
For a rectangular or square lawn, simply multiply the length by the width in metres. For L-shaped or curved lawns, break the area into smaller geometric shapes, calculate each individually, and add the totals together. A measuring wheel or a long tape measure makes this much easier.
Our calculator is designed to handle common units like g/m² and kg/100m². If your product uses different measurements, such as lbs per 1,000 sq ft, you may need to do a quick conversion first. A simple unit converter can help, or check the product's website for metric equivalents.
Yes, absolutely. Applying too much fertiliser – particularly products high in nitrogen – can cause fertiliser burn, which appears as yellow or brown streaks and patches. It can also lead to excessive top growth at the expense of root development, making your lawn less resilient over time.
Most lawns benefit from two to four applications per year. A typical schedule involves a spring feed, an optional early summer top-up, and an autumn feed. Avoid applying more frequently than the product label recommends, as this can lead to build-up and imbalances in the soil.
Yes. Simply use the application rate from your liquid fertiliser's label (usually expressed in ml per litre of water per m²) and enter the values accordingly. The same principle applies – area multiplied by application rate gives you the total quantity needed.