Water Soluble Fertilizer Calculator

Mix a precise nutrient solution at a target ppm of nitrogen.

How the Math Works

The formula calculates the grams of fertilizer needed to achieve a specific nutrient concentration in water. It starts with the desired ppm (parts per million), which represents milligrams of nutrient per liter of water. Multiplying ppm by liters gives the total milligrams required. Dividing by 1000 converts milligrams to grams. Finally, dividing by the fertilizer's nitrogen percentage (as a decimal) adjusts for the fact that the product isn't pure nitrogen. For example, to get 100 ppm in 10 liters with a 20% N fertilizer: (100 × 10) ÷ 1000 ÷ 0.2 = 5 grams.

Practical Applications

To use the calculator, input your target ppm (e.g., 150 for leafy greens), the total liters of water in your reservoir, and the N% listed on your fertilizer's label. The result tells you exactly how many grams to dissolve. For instance, 25 liters of water at 200 ppm using a 10% N fertilizer requires (200 × 25) ÷ 1000 ÷ 0.1 = 50 grams. Always mix thoroughly and verify calculations with a EC meter for precision.

Day-to-Day Use

This tool ensures plants receive optimal nutrition while preventing costly mistakes. By matching ppm to crop needs, you avoid nutrient burn from over-fertilizing or stunted growth from deficiencies. It simplifies daily tasks like mixing hydroponic solutions or garden watering, saving time and money. Whether growing herbs indoors or tomatoes outdoors, precise measurements lead to healthier harvests and reduce wasted fertilizer runoff into drains.

Worked example

150 ppm N in 1 gal with 20-N fertilizer → ~2.84 g.

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