Water-Soluble Fertilizer Calculator — Mix by g/L or ppm
Enter your tank volume, target nutrient concentration (g/L or ppm) and fertilizer purity to find exactly how many grams to dissolve — plus effective ppm, kilograms, and approximate dilution ratio.
L
Concentration unit
%
Weigh this mass into the tank and top up to the target volume
- 1
Raw fertilizer mass
2 × 100 = 200Concentration (g/L) × volume (L) = grams of pure nutrient. - 2
Purity-adjusted mass
200 ÷ 1 = 200
How does this calculator work?
Fertilizer to add (g) = target g/L × tank volume (L) ÷ (purity/100). For ppm targets divide ppm by 1 000 first. Typical hydroponics: 1–3 g/L (1 000–3 000 ppm). Calibrate with an EC meter after mixing. Pure salts like calcium nitrate or MKP need no purity correction.
Formula
How this is calculated
To prepare a fertilizer solution at a chosen concentration, you weigh out a mass of fertilizer and dissolve it in the target volume of water. The fundamental relationship is: mass (g) = target concentration (g/L) × volume (L). If the target is expressed in ppm (milligrams per litre), divide by 1 000 first to convert to g/L before multiplying by volume.
If the fertilizer product is not 100% pure — for example, a 90% technical-grade product or a multi-nutrient blend where the N+P+K percentages sum to less than 100% — divide the required pure-ingredient mass by the purity fraction (purity% ÷ 100) to find the actual product mass to weigh. Most water-soluble analytical-grade or technical-grade fertilizer salts (calcium nitrate, monopotassium phosphate, potassium sulfate, magnesium sulfate) are 98–100% pure; leave purity at 100% unless the label specifies otherwise.
The approximate dilution ratio (1 : X) is reported for reference; it assumes a concentrated stock solution mixed into a larger water volume. In practice, always calibrate finished nutrient solutions with an electrical conductivity (EC) meter, since EC correlates with total ion concentration. Common hydroponic EC targets are 1.0–2.0 mS/cm for leafy greens and 2.0–3.5 mS/cm for fruiting crops (roughly 640–700 ppm per mS/cm, depending on the fertiliser salt).
Frequently asked questions
Leafy greens and herbs run well at 1.0–1.5 g/L total dissolved fertiliser (roughly 1 000–1 500 ppm or 1.5–2.5 mS/cm EC). Fruiting crops such as tomatoes and peppers need 2–3 g/L (2 000–3 000 ppm, 3–4.5 mS/cm). Seedlings and cuttings prefer dilute solution (0.2–0.5 g/L).
In horticulture, ppm means milligrams of dissolved fertilizer per litre of solution (mg/L). An EC meter measures total dissolved ions: a rough conversion is 1 mS/cm ≈ 640–700 ppm, though the exact factor varies by the salt used. EC is the preferred field measurement because it is fast and non-destructive.
Always add fertilizer into water, not the other way round — this prevents dangerous splashing and ensures proper dissolution. For multi-part systems, never mix concentrated stock solutions together before diluting; certain combinations (e.g. calcium with phosphate or sulfate) precipitate immediately. Add each part separately to the main water volume.
Also known as
TG we-Calculate Editorial Team. (2026). Water-Soluble Fertilizer Calculator — Mix by g/L or ppm [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/water-soluble-fertilizer-calculator
TG we-Calculate Editorial Team. "Water-Soluble Fertilizer Calculator — Mix by g/L or ppm." TG we-Calculate. 2026. https://we-calculate.com/calculator/water-soluble-fertilizer-calculator.
TG we-Calculate Editorial Team, "Water-Soluble Fertilizer Calculator — Mix by g/L or ppm," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/water-soluble-fertilizer-calculator
@misc{wecalculate_water_soluble_fertilizer_calculator, title = {Water-Soluble Fertilizer Calculator — Mix by g/L or ppm}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/water-soluble-fertilizer-calculator}}, year = {2026}, note = {TG we-Calculate} }
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