Calculate how much granular fertilizer to apply over an area at a given rate.
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Use this calculator to turn a bag rate in grams per square metre into the mass of product needed for a bed, lawn, or plot. It is a simple area × rate conversion for granular or other products labelled in g/m². For mixing a water-soluble fertilizer to a nitrogen target, use a water-soluble fertilizer calculator instead.
The calculation is: product mass = area × rate. Area can be entered in square metres (m²) or square feet (ft²); square feet are converted to square metres before multiplying. The rate is always in grams per square metre (g/m²). Convert from kg/ha if needed: 1 kg/ha = 0.1 g/m². The product mass is shown in grams (g), ounces (oz), or pounds (lb).
This is the labelled product mass, not a nutrient (N, P, or K) calculation. It does not account for overlaps, edges, or losses.
Area: The bed, lawn, or plot you will cover, in m² or ft².
Rate (g/m²): The label rate in grams per square metre.
Product: Total mass of fertilizer to spread over the entered area.
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