🧪 Water Soluble Fertilizer Calculator
Calculate exactly how much water-soluble fertilizer to dissolve in your water to hit a target nutrient concentration in parts per million (ppm).
What this calculator does
Water-soluble fertilizers are labeled with a nutrient percentage (like 20-20-20), and growers often target a specific nutrient concentration in parts per million (ppm) for feeding plants. This calculator converts a target ppm into the actual amount of fertilizer to dissolve.
How the math works
Ppm is equivalent to milligrams of nutrient per liter of water. The calculator converts your water volume from gallons to liters (1 gallon = 3.785 liters), multiplies by the target ppm to get the milligrams of nutrient needed, then divides by the fertilizer’s nutrient percentage to find the total grams of fertilizer product required, since only that percentage of the product is the active nutrient.
The teaspoon conversion is approximate since fertilizer powders and crystals vary in density between brands; for precise mixing, weighing with a gram scale is more reliable. This tool is for general gardening and horticulture planning purposes.